007 Postgres Command Line : psql : Create a function that returns a single value

As per the nature of recursion a function is a variable is a function.

Previously in 005 and 006 we wrote functions that returned subsets of queries they were effectively dynamic queries where I entered a parameter that was used in a select query. This effectively meant that although the function was returning a variable this was a query of a select statement.

What if we wish just to return a single value as in say translate centigrade to fahrenheit or some other calcuation.

In such case you simply state the function should return a variable and you state the variable type.

eg

CREATE FUNCTION add(integer,integer) RETURNS integer
AS 'SELECT $1 + $2;'
LANGUAGE SQL
IMMUTABLE
RETURNS NULL ON NULL INPUT;

There are a few interesting things here which should be born in mind

  • In this case the addition is performed in SQL
  • I have to specifically name the language of the calculation (SQL) which suggests that if you stated another language it might accept it!
  • You still need to select the function to run it. This indicates that postgres 9.5 doesn’t executve functions as per some environments (ms access for example) – I have read that version 11 changed this and allows you to execute or perform a function. Ms Access you don’t even need to write execute simply the name of the function with the integers.
  • Variables are refererred to as to their input position unlike VBA where you dimension the variable and give it a name. I am unclear at the moment the advantages of the former or later but it is interesting nonetheless. I first came across something similar with autohotkey.
  • 006 Postgres Command Line : psql : Identify definition of a Function

    In 005 when last we left our intrepid explorers we were wondering if having defined an inline table that contains the definition of the selection purely in the user defined function how do we see what that selection is as it might not be a presently defined object. SetOF references an object we can execute independently of the function Table() – does not.

    Well apparently magically you can run the following.

    \ef public.getrecords

    And a notepad will open with the UDF code in it.

    Bright people think of everything.!

    005 Postgres Command Line : psql : Create a User Defined Function and Identify its creation and then Drop it.

    Like all platforms it is possible to create bespoke functions in Postgres

    For the following I assume;
    1. Postgres 9.5 is installed with the server running (syntax should be the same for other versions)
    2. A database called exampledb has been created
    3. In this database there exists table called t001landparcels with some records and a field called PKID
    4. You are logged into the exampledb with a username called general that has been granted CREATEDB role.
    5. You are in psql

    The following can be used to create a simple function

    CREATE FUNCTION getrecords(int) RETURNS SETOF t001landparcels AS $$
    SELECT * FROM t001landparcels WHERE pkid <= $1;
    $$ LANGUAGE SQL;

    If you have been careful and done this exactly the same with my initial assumptions it should return

    CREATE FUNCTION

    This tells us that the functioned has been created this will now exist in the schema the table is as a permanent addition.

    We can identify the function by either listing all the functions and scrolling through

    \df public.*

    or listing the individual function

    \df public.getrecords

    This should return your newly created function

    Now to run the function – unlike MS Access you can’t simply run the function you need to allocate it to a select statement.

    SELECT * FROM getrecords(2);

    This should return everything you are looking for.

    Now you should be able to drop the function using the following SQL

    DROP FUNCTION getrecords(int);

    Note how you have to define the function with its parameter I have read (no idea whether its true) that in version 10 of postgress you can simply use

    DROP FUNCTION getrecords;

    Writing code in psql does require accuracy so getting things to work does usually involve some experimentation. I have removed much of this from my screenshots!

    An alternative is as follows

    CREATE FUNCTION getrecords(int) RETURNS TABLE (pkid integer, parcelname text) as $$
    SELECT pkid, parcelname FROM t001landparcels WHERE pkid <=$1;
    $$ Language SQL;

    This appears to result in the same answer I am not clear what the difference is yet – note the result would have been the same if I had defined the table with the additon of a geometry column.

    Note I dropped the old getrecords function before I created this one. Not sure what would have happened if I had tried to create one over the other.

    I found this second method in stackoverflow when investigating functions with the following to me slightly mysterious quote

    This is effectively the same as using SETOF tablename, but declares the table structure inline instead of referencing an existing object, so joins and such will still work.

    Which sounds to me as important but I’m struggling at present to understand its meaning!

    Stackoverflow discussion

    I will investigate later but what I think he is talking about is that you don’t need to have a defined object before hand eg in setof this is
    SETOF t001landparcels

    I quite often like to have things broken down rather than all in functions and it might prefer to have it as a setof something that I can more clearly see.

    Which leads me to my next question how do you get the definition of a function see 006

    004 Postgres Command Line : psql : Create a spatially enabled table

    For this you will need to have a version of Postgres Database engine installed and running and you will need to have created a database which has the PostGis extension installed.

    Open psql
    Login to the database you wish to create the table in

    type the following

    CREATE TABLE t001landparcels (PKID SERIAL PRIMARY KEY, PARCELNAME VARCHAR(50), GEOM GEOMETRY(POLYGON,27700));

    Here I do this and then check on the tables with the \dt command before inspecting the columns itself using the \d command.

    and here I open up QGIS and link to my local postgres instance and the exampledb database;

    and here I connect to it and draw a polygon. If you are wondering where it is this is InchKeith in the Firth of Forth and island very visible from George Street in Edinburgh. If you have flown into Edinburgh you will have flown almost over it.

    and here after having digitised a single polygon I look at the contents of the table

    SELECT count(*) FROM t001landparcels;

    Produces the more helpful count of records in the table.

    002 Postgres Command Line : psql : Enabling extensions (PostGIS) to a database

    So you have an existing database in PostGres that you wish to add the PostGIS extension to.

    You will need to be logged in with a username that has superuser privileges.
    Here let me do this using the postgres default account that on my instance has superuser access.

    Here rather than logging in at the start I am choosing to change the connection to a different database

    This is done by using

    \c DatabaseName;

    or

    \connect DatabaseName;

    Please note that the semicolon is vital in performing the instruction.

    The way I have discovered to do this is by opening the database and then allocating the postgis extension to the database once it is open.

    Let us first examine the tables in our blank database before the extension is enabled.

    \dt

    Now let us enable the extension.

    CREATE EXTENSION postgis;

    Let us now examine the database tables

    \dt

    Enabling the PostGIS extension adds this table along with the ability to add geometry types of varaibles within tables.

    001 Postgres Command Line : psql : Getting Started with Postgres

    I am just getting into PostGres and here are some rough notes for my reference.

    Assuming you have a postgres admin account you want to sign in first of all and create a database

    To find the command line go to search in Windows and type psql

    Ensure that your postgres engine is running firstly

    You should be presented with the following

    There are default connections to the local host keep hitting these initially until you reach the following;

    You will now need to know your password enter it here and press return

    I will deal with the warning message further in the post – but a lot of people experience this message so I wanted to keep it in at present.

    From my initial investigations as ever it is a good idea to restrict users to particular privileges at this level I am not being particularly refined – I would like to have a poweruser role that I can allocate to people and give this a defined password.

    Signing in you can check out the roles and users as follows – on starting up a new instance you may well see something like this \du

    So here I try and set up a user called general and create a role called general which I give create DB rights

    I would recommend something stronger than the classic password password.

    Issuing the \du command again we get to see the roles

    Now we can close down and go back in but this time login as username general by altering the appropriate item when asked.

    Note how the =# characters have been replaced by => this appears to denote the non superuser sign in.

    To identify what username you are logged in as type \c at the prompt

    My investigations suggest that the # sign denotes that you are logged into the database as superuser.

    So first of all lets get rid of that annoying warning message when you log in at psql

    I am running Postgres version 9.5 your version may vary but you can remove the warning by editing runpsql.bat file every version of postgres has this file and it will be located in the version equivalent directory to 9.5 for me.

    C:\Program Files\PostgreSQL\9.5\scripts

    Add the line

    cmd.exe /c chcp 1252

    as per underline and save the file

    Now fire up psql as usual you should get the following

    It should be noted that if you REM out the SET statements you can choose login with particular server / localhost / database / port and username presets which may be useful if you find yourself constantly going into a particular database as a particular user.

    Here you see that the warning note has stopped.

    It should be noted that using the general username you will NOT be able to create Databases

    In order to CREATE databases you will have to be signed in with a username with sufficient privileges here I am in as postgres and I create a database called ExampleDB

    You can see that on carrying out a successful command we usually see a repeat of the command.

    To get a list of all databases in the instance type

    \l

    It can be seen that despite typing the name in capitals the database has been created in lower case this seems to be a feature of commandline. If you desperately want capitals you may need to go to pgadmin tool.

    I think I’ll end it there for now.

    SQL Azure – Group child records by parent in order

    Lets say we have two tables

    A site parent table T001 consisting of two fields
    PKID
    Sitename

    And a planning application child table T002 consisting of three fields
    PKID
    PKIDT001
    PlanRef

    We have the following records in the parent table T001
    1 – Site01Green
    2 – Site02Red
    3 – Site03Blue

    And the following related children in the planning application table T002;
    1 – 1 – 2019/098
    1 – 1 – 2018/032
    1 – 2 – 2017/987
    1 – 3 – 2015/100
    1 – 3 – 2014/456
    1 – 3 – 2014/657

    And we would like to write a query that would create a list combining the two tables showing all the planning applications for each site listed in order.

    This is the list we are aiming at
    1 – 2018/032,2019/098
    2 – 2017/987
    3 – 2014/456,2014/657,2015/100

    Using SQL Server 2017 or later (including SQL Azure) the following will work

    CREATE VIEW [dbo].[View01Sitesandtheirplanapps] AS SELECT PKIDT001, STRING_AGG(PlanRef,',') WITHIN GROUP (ORDER by PlanRef ASC) as PlanRefs
    From dbo.T002
    GROUP BY PKIDT001;

    This can then be combined in a separate view that will include the sitename should it be required – this is a tremendous example the structure of which I will be using often.

    Lighthouse – Performance statistics for Web Sites

    As part of the general move towards the web I continue to investigate and learn about web development. An important aspect for any developer considering how to serve programs to clients and colleagues with as little resistance as possible – is Speed – users will be clicking these things potentially tens of times a minute and waiting to go from one screen to another signifcantly impacts their productivity. No wonder then we are hearing so many stories about dramatic improvements in site success by improving load speeds – but how to measure web site speed accurately? At work and for desktop applications I have resorted to downloading a stopwatch onto my android phone which can be quite useful if there are consistent and substantial differences in speed – still however a somewhat blunt and inaccurate tool.

    So the other day I was again investigating how to better improve the delivery of web sites through the installation of web sites using the new Google Progressive Web Application paradigm.

    I discovered within Chrome there is an Audit feature beneath the inspection option.

    To use this open the web page you are interested in measuring using Chrome ensuring that it is a standard Chrome window (and not the PWA window)

    Right click and then go for inspect then select the Audits option as shown below.

    At which point you should be presented with the following

    Now hit the Run audits button at the bottom

    We see the statistics in the top right. From my initial running of this on several of my sites the metrics on
    Progressive Web App
    Accessibility
    Best Practices
    SEO
    Seems to be fairly consistent in ranking sites.

    Performance seems to vary every time you run it even if you are on the same page and url.
    Here for example is me running the same audit literally five minutes after the last picture.

    So all in all definitely an improvement in metrics but with some of the metrics varying so much from run to run it may still be better for giving a general indication of performance overtime than anything else. I have just upgraded this site to WordPress 5.0.1 although the theme is still from 2010. It should be noted my MS Access applications still transfer between forms within fractions of a second, so fast in fact that I am unable to measure them. Websites are getting better and there are sites now that are very fast. Still some way to go though before they can beat the blistering speed of desktop.

    I have started looking at new themes for the site but I find I like a lot about this theme and am having trouble finding anything I am quite as happy with.

    MS Access Function CreateSimpleStrings()

    A simple function that will loop through and create strings that add a number to a simple string. This string will then be used to create update queries. The same could be done in Excel or any other spreadsheet option but this stores the queries nicely and neatly into a table.

    In this instance you want to have created a table called
    T002ResidentialSearch

    Which has the following fields
    ResidentialString
    Houses

    Public Function CreateSimpleStrings()
    
    Dim i As Integer
    Dim rs As DAO.Recordset
    Dim db As DAO.Database
    Set db = CurrentDb
    
    Set rs = db.OpenRecordset("T002ResidentialSearch")
    
    For i = 2 To 100
    
    With rs
    rs.AddNew
    rs!ResidentialString = "Erection of " &amp; i &amp; " houses"
    rs!Houses = i
    rs.Update
    End With
    Next i
    
    rs.Close
    
    MsgBox "Complete"
    
    End Function

    Visual Basic Script that can be used to rename a file

    Here I am trying to automatically load log files into a MS Access file. Log files are actually txt files which need their extension changed if like me you wish to automate their import into MS Access. The following Visual Basic Script takes a file called FS_LS.log and changes it to FS_LS.txt. (I have another function that then takes this file and imports it into an MS Access application.

    For safety this script creates a copy of the FS_LS log and renames it with a txt extension combining hours and minutes into the title. Thus it needs to be run one minute apart otherwise it will throw an error.

    For testing purposes I have the following line

    Fso.Copyfile "C:\Users\mark\Documents\vbs\" & vardatefile, "C:\Users\mark\Documents\vbs\" & vardatefile3

    If you don’t have a feed to some kind of constant stream of log files this will copy the txt back to a log file ready to be copied again.(something I found useful for testing). Now next you want to call this from within your MS Access application prior to your data import function using the previously posted function.

    Dim Fso
    Dim vardatefile
    Dim vardatefile2
    Dim vardatefile3
    Dim varhoursleft
    Dim varminsright
    Dim varnow
    
    varnow= FormatDateTime(now,4)
    varhoursleft = left(varnow,2)
    'msgbox varhoursleft
    
    varminsright = right(varnow,2)
    'msgbox varminsright
    Set Fso = WScript.CreateObject("Scripting.FileSystemObject")
    vardatefile2 = "FS_LS.txt"
    vardatefile3 = "FS_LS.log"
    vardatefile = "FSLS-" & varhoursleft & varminsright & ".txt"
    Fso.MoveFile "C:\Users\Mark\Downloads\FS_LS.log", "C:\Users\Mark\Downloads\" & vardatefile
    Fso.Copyfile "C:\Users\Mark\Downloads\" & vardatefile, "C:\Users\Mark\Downloads\" & vardatefile2
    'Fso.Copyfile "C:\Users\Mark\Downloads\" & vardatefile, "C:\Users\Mark\Downloads\" & vardatefile3
    
    Set FSO = nothing

    Chrome polishes its menu setup – Chrome Shortcuts now run web pages in application mode

    PS – UPDATE AT 10 NOVEMBER 2018 – I MAY TAKE THIS POST DOWN AS MY CHROME VERSION ON WINDOWS 10 NO LONGER GIVES ME THE OPEN IN NEW WINDOW TICK AND JUST CREATES A SHORTCUT ON THE DESKTOP NOW.

    THANK YOU STACK OVERFLOW UPDATE appears others have figured out how to get round this see
    Link

    PPS UPDATE AT 19 APRIL 2019 – Google have re-instated open in new window Icon. Great that common sense has prevailed and an interesting example of how quickly software development changes… Below should be broadly valid again.

    Much like Google Maps changing the projection to a proper globe on zoom out. I noticed Google made a very slight change to their browser application which is a nice demonstration of how Google are constantly trying to improve their interfaces to make them more intuitive. At some point they altered the menu setup for creating web pages in application mode – I had written a post about the former method (see my post here) For those unfamiliar with this it is a really nice way of displaying web pages in what appears an application like window (ie no url bar or tabs). Comparing the two you can see that they have simply changed the menu from Add to desktop to Create Shortcut. Its a nice demonstration of the small improvements that are continually being made to the browser.

    I had noticed that all my icons that I had formally created using the former application mode had stopped working.
    Didn’t think much of it at the time but I think that must have been the date when Chrome changed over their code.

    It should be noted that simply dragging the web page onto the desktop from the chrome browser window still gives the old windows shortcut what we want here is the Google shortcut. So here is how I do it.

    Then select the following

    Select create shortcut and a new dialog should appear

    Name it and there you go

    Now you get a nice icon on your desktop related to the site and what’s more when you open it up there is no address bar and within the taskbar you get the correct icon for the website see below example.

    MS Access Function – import all CSV files from a directory with the same structure into a single table

    This is a really nice function that can be used to place all data from multiple CSVs (with the same structure) into a single table.

    Here I use the Ordnance Survey’s excellent Code Point data set that gives postcodes in the UK along with eastings and northings as an example – This lists each postcode in the UK along with further administrative categories. Apologies to anyone from outside of the UK that may not be able to access these files I hope the demonstration is still useful. For those wishing to try pleased follow the links.

    After download you will see the problem each postcode is in a separate CSV

    Ordnance Survey Open Data Code Point UK Postcodes

    After a short process to request the download including filling out your name you should be sent an email to download the data. This will consist of a zip file of two directories one named DOC one named DATA the DATA directory contains a subdirectory called CSV which at May 2018 for my download consisted of 120 csv files.

    Opening a single file ( in this case Edinburgh eh ) we see

    I’ve already figured this out here , but there are 10 fields here (some are blank in my example)

    Here I create a table called T01CodePointCombined with 10 fields marked
    F1 through to F10
    Note if you don’t create the table this function is so powerful it will do it for you

    I then create a module and ensure that all the CSV files I wish to import are in a single directory here “C:\Users\Mark\Documents\CodePoint\Data\CSV\”

    Public Function ImportAllFiles()
    
            Dim strPathFile As String, strFile As String, strPath As String
            Dim strTable As String
            Dim blnHasFieldNames As Boolean
    
            ' Change this next line to True if the first row in csv file
            ' has field names
            blnHasFieldNames = False
    
            ' Replace C:\Users\Mark\Documents\CodePoint\Data\CSV\ with the real path to the folder that
            ' Now place the location of where the csvs are within the brackets below
            strPath = ""
    
            ' Replace tablename with the real name of the table into which
            ' the data are to be imported
            strTable = "T01CodePointCombined"
    
            strFile = Dir(strPath & "*.csv")
            Do While Len(strFile) > 0
                  strPathFile = strPath & strFile
    
                  DoCmd.TransferText _
                    TransferType:=acImportDelim, _
                    TableName:=strTable, _
                    filename:=strPathFile, _
                    HasFieldNames:=blnHasFieldNames
    
            ' Uncomment out the next code step if you want to delete the
            ' csv file after it's been imported
            '       Kill strPathFile
    
                  strFile = Dir()
            Loop
    
            MsgBox "Finished"
    
    End Function

    Points to note make sure all csv are closed when you run it. That’s about it takes less than 5 minutes to move all the records from those 120 files into a single table within an MS Access Database.
    After import if it’s gone correctly you should have in the region of 1.7 million records in T01CodePointCombined.

    MS Access Function – Scan through a directory and write list of files to a table

    Pretty much as the title

    Ensure you have a table called tblFiles with one field called Filename

    Here I am finding all files in folderspec = “C:\Users\Mark\Documents\CodePoint\Data\CSV”

    Alter as appropriate

    Public Function ShowFolderList()
    Dim fs, f, f1, fc, s
    Dim rs As DAO.Recordset
    Dim folderspec
    
    Set rs = CurrentDb.OpenRecordset("tblFiles")
    
    folderspec = "C:\Users\Mark\Documents\CodePoint\Data\CSV"
    
    Set fs = CreateObject("Scripting.FileSystemObject")
    Set f = fs.GetFolder(folderspec)
    Set fc = f.Files
    
    For Each f1 In fc
        rs.AddNew
        rs.Fields("FileName") = f1.Name
        rs.Update
    Next
    
    Set rs = Nothing
    
    MsgBox "Finished"
    
    End Function

    MS Access – Code Snippets for Navigating using Internet Explorer

    Waiting for a web page to load

    While ie.Busy
    DoEvents
    Wend

    Selecting differing radio buttons

    Dim ieRadio As Object
    Set ieRadio = ie.Document.all
    ieRadio.Item("datetype")(1).Checked = True

    A function that can be used to delay action before an action in code (Not web specific). Here I set to 1 second

    Public Function Await1()
    Dim time1 As Variant
    Dim time2 As Variant
    
    time1 = Now
    time2 = Now + TimeValue("0:00:01")
        Do Until time1 >= time2
            DoEvents
            time1 = Now()
        Loop
    
    End Function

    Split a string of text into a 1 dimensional array with splitting occurring at returns.

    Dim strArray() as String
    Dim strtoParse as String
    Dim intCount as Long
    
    'here I taken an imaginary recordset and set the string to parse from the text value in the recordset
    strtoParse = rs!Text
    strArray = Split(strtoParse, vbNewLine)
    
    'a simple loop that will count the number of values in the array (1 dimensional)
    For intcount = LBound(strArray) To UBound(strArray)
          MsgBox Trim(strArray(intCount))
       Next

    Find a string in an array note the complete string needs to be found not a part within one of the array parts.

    Private Function WhereInArray(vArrayName As Variant, vStringtoFind As String) As Variant
    Dim i As Long
    For i = LBound(vArrayName) To UBound(vArrayName)
        If vArrayName(i) = vStringtoFind Then
            WhereInArray = i
            Exit Function
        End If
    Next i
    'if you get here, vStringtoFind was not in the array. Set to null
    WhereInArray = Null
    End Function

    Show whats in which Array cell – where n is a number equal to the value of a cell
    So eg strArray(60) would show the value in 60th cell note arrays start from 0

    MsgBox strArray(n)

    Copy the HTML of a web page to a variable

    my_StrVariable = ie.Document.body.innerHTML

    Filter out much of the HTML formatting and only put inner text into a variable

    my_StrVariable = ie.Document.body.innerText

    Replace with spaces with less spaces till 2 and 3 spaces are replaced by 1 space

    Function ThreeTwo(ByVal parmString As String) As String
        Dim strTemp As String
        strTemp = parmString
    
        Do Until InStr(strTemp, "   ") = 0
            strTemp = Replace(strTemp, "   ", " ")
        Loop
    
        Do Until InStr(strTemp, "  ") = 0
            strTemp = Replace(strTemp, "  ", " ")
        Loop
        ThreeTwo = strTemp
    End Function

    Click on a button if all you know is its class name

    Dim e
    Set e = ie.Document.getElementsByClassName("button primary")(0)
    e.Click

    Identify sites and how often they are visited
    labpix.online/rounduptheusualsuspects.org
    Look at any site
    http://labpix.online

    Take a look at the robots.txt of a site
    https://www.theregister.co.uk/robots.txt

    https://www.ebay.co.uk/robots.txt

    MS Access Front End – Linked to PostGreSQL back end – a simple walk through using Access 2003

    As I have indicated before MS Access makes a brilliant ETL tool. Important in this is being able to connect to different databases. I have set out how to connect to MySQL and SQLAzure before – the following sets out how to connect to PostGres.

    To follow along you will either need PostGres installed on your local computer or alternatively all required connection parameters to a database in the cloud or on your lan.
    PostGres Download

    You will also need to Download and install a PostGreSQL ODBC driver – these are available at the following(March 2018).

    PostGres ODBC Drivers

    Scroll down the list – here I went to the bottom and obtained x64 version – MSI are downloaded (Microsoft Windows Installer files) – Install and then move to the next step.

    Next create a blank database and right click in the white area to reveal a menu – select link tables.

    You should now be presented with the Select Data Source dialog. Here I hit New…

    This brings up the Create New Data Source dialog which lists database drivers scroll down through the list to PostgreSQL Unicode and select

    Give your DSN an appropriate name and then go back to link table but this time rather than hitting the new button navigate to where you saved your DSN and select it and press OK.

    The ever important parameters – you just need to know these – if you set up PostGres and you can get in through PG Admin selecting properties on the database should reveal the panel that will give you some guidelines. You may wish to double click on the image below so you can get a closer link of how I place my parameters in. I have opened the PGAdmin dialog here and placed it alongside the MS Access database window to show the properties I am transferring across.

    Hitting OK should present you with the tables in your database.

    And here is a demonstration with the link in place along with the table open and a simple form shown.

    MS Access Function Collection that can be used to Generate Housing Forecast Figures

    Apologies if you are coming here for the first time. This post is a somewhat dense domain specific holding post for some work I did at the weekend to pull together some thoughts.

    I was thinking that if I had a list of all sites in the UK I should be able to generate a phasing for each of them based on maybe the area of the site. This would automatically create a general housing land audit for any site that I should put in. I thought I’d try and see if I could write a set of functions that might generate phasing by site. Given that you can get an estimate of the housing boundaries from open street map and that you can get their area it would be possible to get an estimated number of houses per site which could then be used to phase. Going further if you were ever to know planning permission dates you could more accurately use this as a date from which to start phasing.

    Ensure you have three tables
    T01Sites (PKID, TotalNoHouses, DecisionDate)
    T02HousePhasing (PKID, SiteFKID, Year, Completions)
    T03 (PKID, TotalNoHouses, DecisionDate, YearofDecision, YearofStart, YearSpread)

    T02 is the phasing child table of T01 and T03 is a holding table for a make table that will hold a randomised spread over which you wish to phase the total no of houses. It also randomly predicts when the housing will start on site.

    And three queries

    Q01 – Make Table Query

    SELECT T01Sites.PKID, T01Sites.SiteName, T01Sites.TotalNoHouses, T01Sites.DecisionDate, Year([DecisionDate]) AS YearofDecision, CalculateintYearStartFULLPP([YearofDecision]) AS YearofStart, intYearSpread([TotalNoHouses]) AS YearSpread INTO T03
    FROM T01Sites;

    Q02 – Select Query

    SELECT T03.PKID, T03.SiteName, T03.TotalNoHouses, T03.DecisionDate, T03.YearofStart, T03.YearSpread, Int(T03!TotalNoHouses/T03!YearSpread) AS PerYearSpread, [TotalNoHouses] Mod [YearSpread] AS Remainder
    FROM T03
    WHERE ((([TotalNoHouses] Mod [YearSpread])=0));

    Q03 – Select Query

    SELECT T03.PKID, T03.SiteName, T03.TotalNoHouses, T03.DecisionDate, T03.YearofStart, T03.YearSpread, Int(T03!TotalNoHouses/T03!YearSpread) AS PerYearSpread, [TotalNoHouses] Mod [YearSpread] AS Remainder
    FROM T03
    WHERE ((([TotalNoHouses] Mod [YearSpread])>0));

    VBA Function list
    The first function randomises the spread in years over which construction might happen on an individual housing site based on the total number of houses on the site.

    Public Function intYearSpread(TotalNoHouses As Integer) As Integer
    
    If TotalNoHouses < 2 Then
    
    intYearSpread = 1
    
    ElseIf TotalNoHouses = 2 Then
    
    intYearSpread = Int((TotalNoHouses) * Rnd) + 1
    
    ElseIf TotalNoHouses > 2 And TotalNoHouses < 9 Then
    
    intYearSpread = Int((TotalNoHouses - 2 + 1) * Rnd + 1)
    
    ElseIf TotalNoHouses >= 9 And TotalNoHouses <= 40 Then
    
    intYearSpread = Int((4) * Rnd + 1)
    
    ElseIf TotalNoHouses >= 41 And TotalNoHouses <= 80 Then
    
    intYearSpread = Int((8 - 4 + 1) * Rnd + 4)
    
    ElseIf TotalNoHouses >= 81 And TotalNoHouses <= 200 Then
    
    intYearSpread = Int((8 - 4 + 1) * Rnd + 4)
    
    ElseIf TotalNoHouses >= 201 And TotalNoHouses <= 400 Then
    
    intYearSpread = Int((10 - 6 + 1) * Rnd + 6)
    
    ElseIf TotalNoHouses >= 401 And TotalNoHouses <= 800 Then
    
    intYearSpread = Int((12 - 8 + 1) * Rnd + 8)
    
    Else
    
    intYearSpread = Int((20 - 10 + 1) * Rnd + 10)
    
    End If
    
    'MsgBox intYearSpread
    
    End Function

    The first of the next three functions is used in the query to identify a year from which phasing on site will start. I wrote two further functions with the thought that in the future I could create a switch that would allow alternative site starts depending on whether a site has planning permission and depending on the type of planning permission. For example full planning permission would mean starting within three years of the granting of planning permission whereas outline would push it to between 3 and 6 years. A site with an LDP allocation would start further into the future.

    Public Function CalculateintYearStartFULLPP(intDecisionDateYear As Integer) As Integer
    
    CalculateintYearStartFULLPP = intDecisionDateYear + (Int((3 - 1 + 1) * Rnd + 1))
    
    End Function
    
    'Not used at present
    Public Function CalculateintYearStartPPPP(intDecisionDateYear As Integer) As Integer
    
    CalculateintYearStartPPPP = intDecisionDateYear + (Int((6 - 3 + 1) * Rnd + 3))
    
    End Function
    
    'Not used at present
    Public Function CalculateintYearStartLDP(intDecisionDateYear As Integer) As Integer
    
    CalculateintYearStartLDP = intDecisionDateYear + (Int((20 - 8 + 1) * Rnd + 8))
    
    MsgBox CalculateintYearStartLDP
    
    End Function

    Function to create phasing IF housing IS perfectly divisible by Year Spread
    GRH is an acronym for Generate Randomised Housing

    Public Function GRHZero() As Variant
    
    Dim db As DAO.Database
    Dim rsSource As DAO.Recordset
    Dim rsPhasing As DAO.Recordset
    Dim intrsSourcePKID As Integer
    Dim intrsSourceYearofStart As Integer
    Dim intYearSpread As Integer
    Dim intPerYearSpread As Integer
    Dim i As Integer
    
    Set db = CurrentDb()
    Set rsSource = db.OpenRecordset("Q02")
    Set rsPhasing = db.OpenRecordset("T02HousePhasing")
    
    If Not (rsSource.EOF And rsSource.BOF) Then
    'There are no records if End of File and Beginning of File are both true
    
    rsSource.MoveFirst
    
    Do Until rsSource.EOF = True
    
    intrsSourcePKID = rsSource!PKID
    intrsSourceYearofStart = rsSource!YearofStart
    intYearSpread = rsSource!YearSpread
    intPerYearSpread = rsSource!PerYearSpread
    
    For i = 1 To intYearSpread
    
    With rsPhasing
    rsPhasing.AddNew
    rsPhasing!SiteFKID = intrsSourcePKID
    rsPhasing!Year = intrsSourceYearofStart
    rsPhasing!Completions = intPerYearSpread
    rsPhasing.Update
    intrsSourceYearofStart = intrsSourceYearofStart + 1
    End With
    
    Next i
    
    rsSource.MoveNext
    
    Loop
    Else
    MsgBox "No Records"
    Exit Function
    End If
    
    rsPhasing.Close
    rsSource.Close
    
    Set rsPhasing = Nothing
    Set rsSource = Nothing
    
    Set db = Nothing
    
    End Function

    Function to create phasing IF housing IS NOT perfectly divisible by Year Spread and a remainder is put on end

    Public Function GRHRemainder() As Variant
    
    Dim db As DAO.Database
    Dim rsSource As DAO.Recordset
    Dim rsPhasing As DAO.Recordset
    Dim intrsSourcePKID As Integer
    Dim intrsSourceYearofStart As Integer
    Dim intYearSpread As Integer
    Dim intPerYearSpread As Integer
    Dim intRemainder As Integer
    Dim i As Integer
    
    Set db = CurrentDb()
    Set rsSource = db.OpenRecordset("Q03")
    Set rsPhasing = db.OpenRecordset("T02HousePhasing")
    
    If Not (rsSource.EOF And rsSource.BOF) Then
    'There are no records if End of File and Beginning of File are both true
    
    rsSource.MoveFirst
    
    Do Until rsSource.EOF = True
    
    intrsSourcePKID = rsSource!PKID
    intrsSourceYearofStart = rsSource!YearofStart
    intYearSpread = rsSource!YearSpread
    intPerYearSpread = rsSource!PerYearSpread
    intRemainder = rsSource!Remainder
    
    For i = 1 To intYearSpread
    
    With rsPhasing
    rsPhasing.AddNew
    rsPhasing!SiteFKID = intrsSourcePKID
    rsPhasing!Year = intrsSourceYearofStart
    rsPhasing!Completions = intPerYearSpread
    rsPhasing.Update
    intrsSourceYearofStart = intrsSourceYearofStart + 1
    End With
    
    Next i
    
    With rsPhasing
    rsPhasing.AddNew
    rsPhasing!SiteFKID = intrsSourcePKID
    rsPhasing!Year = intrsSourceYearofStart
    rsPhasing!Completions = intRemainder
    rsPhasing.Update
    intrsSourceYearofStart = intrsSourceYearofStart + 1
    End With
    
    rsSource.MoveNext
    
    Loop
    Else
    MsgBox "No Records"
    Exit Function
    End If
    
    rsPhasing.Close
    rsSource.Close
    
    Set rsPhasing = Nothing
    Set rsSource = Nothing
    
    Set db = Nothing
    
    End Function

    And the Script to run both the above functions

    Public Function GeneratePhasingRecords()
    
    Call GRHZero
    Call GRHRemainder
    
    MsgBox "Finished"
    
    End Function