Composite SQL Field with null Value Returns Blank

The intent was to join the address fields as a single returned value from a database query select. But I found that if one of these fields was null, the whole returned result was empty.

I had an address, in the usual way, across a number of database fields: address; town ; postcode and county.

I wished o let the database query do the work, joining the fields, as opposed to the VB/C# code.

The SQL query to join these fields as a single composite field value.

Shown below is my first version of the composite field value, derived from the individual address parameters.

‘Street: ‘ + building.address + ‘, Town: ‘ + building.town + ‘, Postcode: ‘ + building.postcode + ” AS Location

My original expectation was that if one of these address fields was null then that part would be shown as blank.

For example with no town the returned entry might be:

Street: Broad Street, Town: , Postcode:  Rg1 1AA

I found that whilst I could readily create a string composed from the individual fields on occasion the result was empty, even though I knew at least one field to have a valid value.

Investigating I showed that if one of the fields was empty (null) then the whole combined field had a null value.

The building location was to show the address, as street, town and postcode.

‘Street: ‘ + building.address + ‘, Town: ‘ + building.town + ‘, Postcode: ‘ + building.postcode + ” AS Location

As can be seen its a simple string addition of the individual fields.

However, if there was no entry in one of the fields, ie. it was null, then the whole result returned as an empty field, as opposed to the single empty entry.

To correct the empty result error I added an isnull test for each field, taking either the database value or an alternative presentational value, In this instance a couple of dashes to indicate that there is no entry.

‘Street: ‘ + ISNULL(building.address,’–‘) + ‘Town: ‘ + ISNULL(building.town,’–‘) + ‘Postcode: ‘ + ISNULL(building.postcode,’–‘) + ” AS Location

Shown above is the previous example with the addition of the isnull.

For our earlier example this gives:

Street: Broad Street, Town: –, Postcode:  Rg1 1AA

Insert string into Database as datetime

Inserting values into a database table I wished to add a date and time.

For this I used a convert

CONVERT(datetime, ’26/05/2014 14:21:00′)

However this will fail where the day value is too high. A value greater than 12 will be taken as an invalid month. Also the day and month will be saved swapped.

The date format should be defined as UK based, d/m/y

For this the country format value is included within the conversion.

CONVERT(datetime, ’26/05/2014 14:21:00′, 103)

In this example using 103 to handle UK date format

Note: also ensure there are no spaces at the start or end of  the enclosed string.

Get Table Foreign Key Details by SQL

How to view the foreign key settings within a database administered using MyLittleAdmin?

Looking to find information about foreign keys between tables, via the control panel for a website I was using MyLittleAdmin to manage the associated database.

I was able to view the keys associated with a particular table but unlike the SQL Management Studio this didn’t allow for key review.

I looked to using t-sql and found this

SELECT
  fk.name AS ForeignKey,
  OBJECT_NAME(fk.parent_object_id) AS FkTable,
  COL_NAME(fkc.parent_object_id, fkc.parent_column_id) AS FkColumn,
  OBJECT_NAME(fk.referenced_object_id) AS ReferencedTable,
  COL_NAME(fkc.referenced_object_id, fkc.referenced_column_id)
  AS ReferencedColumn,
  delete_referential_action_desc AS OnDelete,
  update_referential_action_desc AS OnUpdate
FROM sys.foreign_keys AS fk
INNER JOIN sys.foreign_key_columns AS fkc
ON fk.object_id = fkc.constraint_object_id
WHERE fk.parent_object_id = OBJECT_ID('OurStuff');

which is taken from https://www.simple-talk.com/sql/t-sql-programming/questions-about-primary-and-foreign-keys-you-were-too-shy-to-ask/

By changing the table reference I was able to get the list of keys and their settings.

Turn off Identity Whilst Inserting SQL Table Row

Inserting table rows including the index idents will give an error similar to:

Cannot insert explicit value for identity 
column in table TableName when IDENTITY_INSERT is 
set to OFF.

I was copying the contents of a database table from one installation of DotNetNuke to another.

Wishing to maintain the table structure, parent and child references meant that to best recreate and copy the table I should maintain the existing index identify values.

The table used the table unique identity index to create a parent and child relationship between some of the rows.

To export the table I was able to select all of the table content and display it as a table.

The table of data could then be copied into an editor (Geany) to add the necessary insert SQL.

To properly maintain the table data and allow a true reproduction the interlinking between the rows must be maintained. To adhesive this the index ident must be imported.

A table will automatically assign the route ident when the route is inserted. If the field is included as part of the insert statement the insert will fail with an error.

To overcome the block on the insert into the ident field i turned off the restriction at the start of my SQL insert and restore it again afterwards.

For a table with an orienting set on one of the fields performing a simple insert will fail beaches the identity field doesn’t permit is valid to be set.

To overcome this I top and tailed the insert statements with identity on and off

SET IDENTITY_INSERT GalleryAlbum ON

Insert of table rows SQL

SET IDENTITY_INSERT GalleryAlbum OFF

Convert SQL Field of Type text to nvarchar(max)

To enable database tables to handle the extended character set languages I was looking to convert fields from type text to ntext.

Aware of the pending loss of support for the field types text and ntext I also chose to convert these fields to nvarchar(max).

SQL server 2016 is removing support for field type text and ntext.

In this example table I had a field called body which was of type text.

The field was to retain its name but to be changed to a type which would support a greater international language.

To prepare for SQL server 2016 I chose to also change it to type nvarchar(max).

Given below is the SQL applied to the table portfolio.

alter table dbo.Portfolio add body2 text
go
update dbo.Portfolio set body2 = body
go
alter table dbo.Portfolio drop column body
go
alter table dbo.Portfolio add body nvarchar(max)
go
update dbo.Portfolio set body = body2
go
alter table dbo.Portfolio drop column body2
go

As can be seen above I begin by adding a second field of type text, called body2.

The field body is then copied to this be field body2.

The old field can now be dropped. You may prefer to check at this point that the data has been copied.

Now to create the new version of the body, giving a type of nvarchar(max).

Once more the data is copied. This time back to the body field.

Perhaps another check of the data copy?

And finally deletion of the temporary field.

Details of what’s in and what’s out on SQL server 2016.

MSSQL Table Search and Replace

Consider a database table of posts or pages.

The website address has changed, perhaps from the development URL to the live website

Or maybe the website’s URL is to change from example.co.uk to example.com.

The tables are to be updated, ideally searching and replacing the old value with a new one.

Given below is a search and replace for the table post, replacing the URL entries in the field pbody.

UPDATE
post
SET
pbody = REPLACE(pbody,'example.co.uk','example.com')
WHERE
pbody LIKE '%example.co.uk%'

A search and replace of a MS SQL table replacing a website URL or correcting an error.

List Large Tables

An enlarged DotNetNuke database can affect performance and also be an indication of a more serious issue. Listing table sizes can help to understand and resolve issues.

I have used this piece of SQL to check whether the site log or the event log is over sized on a website.

CREATE TABLE #temp (
table_name sysname ,
row_count INT,
reserved_size VARCHAR(50),
data_size VARCHAR(50),
index_size VARCHAR(50),
unused_size VARCHAR(50))
SET NOCOUNT ON
INSERT #temp
EXEC sp_msforeachtable 'sp_spaceused ''?'''
SELECT a.table_name,
a.row_count,
COUNT(*) AS col_count,
a.data_size
FROM #temp a
INNER JOIN information_schema.columns b
ON a.table_name collate database_default
= b.table_name collate database_default
GROUP BY a.table_name, a.row_count, a.data_size
ORDER BY CAST(REPLACE(a.data_size, ' KB', '') AS integer) DESC
DROP TABLE #temp

The SQL may be executed from either within the DotNetNuke website or, where the website is failing, from the SQL Management Studio.

To run the SQL on the website, as a host user open the page Host > SQL.

List large tables host sql pagePaste the above code into the box and click on Run Script at the bottom of the page.

list-large-tables-host-sql-page-paste-sqlThe tables within the database will be listed together with their associated size, see example listing below:

list-large-tables-host-sql-page-run-scriptAs can be seen the tables from the database are listed  showing their name; row count; column count and data size, listed with the data size descending.

Convert Text to nText

Changing a column having type text to its corresponding type ntext is a little more complicated than changing some of the other field types, for example varchar to nvarchar.

To change a field from type varchar to nvarchar simply requires the column type to be changed, using some code like below:

IF EXISTS (SELECT * FROM dbo.sysobjects WHERE id = object_id(N'{databaseOwner}{objectQualifier}VNTweb_Fruit_Products') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
ALTER TABLE {databaseOwner}{objectQualifier}VNTweb_Fruit_Products
ALTER COLUMN image_large nvarchar(100)
GO

However, the same is not true when changing a column of type text to type ntext. In this case the process is a little longer requiring the creation of a temporary column:

  1. create a temporary column of type ntext
  2. copy the existing column data to the new temporary column
  3. delete the existing column
  4. create a new column (with the original name) of type ntext
  5. copy the contents from the temporary column to the new column
  6. delete the temporary column

Example SQL code for transferring a column of type text to ntext is given below:

IF EXISTS (SELECT * FROM dbo.sysobjects WHERE id = object_id(N'{databaseOwner}{objectQualifier}VNTweb_Fruit_Products') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
ALTER TABLE {databaseOwner}{objectQualifier}VNTweb_Fruit_Products ADD TempDescription ntext
GO
IF EXISTS (SELECT * FROM dbo.sysobjects WHERE id = object_id(N'{databaseOwner}{objectQualifier}VNTweb_Fruit_Products') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
UPDATE {objectQualifier}VNTweb_Fruit_Products SET TempDescription = Description
GO
IF EXISTS (SELECT * FROM dbo.sysobjects WHERE id = object_id(N'{databaseOwner}{objectQualifier}VNTweb_Fruit_Products') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
ALTER TABLE {databaseOwner}{objectQualifier}VNTweb_Fruit_Products DROP COLUMN Description
GO
IF EXISTS (SELECT * FROM dbo.sysobjects WHERE id = object_id(N'{databaseOwner}{objectQualifier}VNTweb_Fruit_Products') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
ALTER TABLE {databaseOwner}{objectQualifier}VNTweb_Fruit_Products ADD Description ntext
GO
IF EXISTS (SELECT * FROM dbo.sysobjects WHERE id = object_id(N'{databaseOwner}{objectQualifier}VNTweb_Fruit_Products') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
UPDATE {objectQualifier}VNTweb_Fruit_Products SET Description = TempDescription
GO
IF EXISTS (SELECT * FROM dbo.sysobjects WHERE id = object_id(N'{databaseOwner}{objectQualifier}VNTweb_Fruit_Products') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
ALTER TABLE {databaseOwner}{objectQualifier}VNTweb_Fruit_Products DROP COLUMN TempDescription
GO

SQL Password Must Change

I have created a number of users and databases using the SQL Server Management Studio. Unfortunately, whilst creating a new user login, unticking of the entries relating to the password policy can be forgotten:

  • Enforce password expiration
  • User must change password at next login

With these entries ticked and enforced an automated login from a CMS website such as DotNetNuke will fail. There is no support for the password change dialogue.

To change the password policy for the account run the following as a new query (top left hand corner)

ALTER LOGIN USERNAME WITH PASSWORD=’PASSWORD’

Where USERNAME is the name of the user and PASSWORD is the new password.

Following this it is now possible to revisit the properties for the user and to uncheck the checkbox for enforce password expiration.

SQL Union Select Join Command

The SQL UNION command is used to gather the entries from two tables which meet the given criteria.

The SQL Union command is used to select entries from two tables It requires that the items in each of the select are in the same order and that each comparable item in the same position is of the same data type and length.

Consider a typical example of two sets of employees located in two different countries, those in England and France:

England – table name =  Users_GB

Ref. (UserId) First Name (FName) Last Name (LName)
006 Peter Smith
008 Steven Jones
023 Ruth Mortimer
034 Kurt Fulmore
184 Linda Loveridge

France – table name = Users_FR

Ref. (UserId) First Name (FName) Last Name (LName)
007 Linda Loveridge
026 Louisa Revel
027 Mark Mitchell
101 Alan Brown
128 James Woodrow

SELECT FName,LName FROM Users_GB
UNION
SELECT FName,LName FROM Users_FR

As given above the command will select distinct entries, where entries are common to both tables only one entry will be returned.

UNION combined table

First Name (FName) Last Name (LName)
Peter Smith
Steven Jones
Ruth Mortimer
Kurt Fulmore
Linda Loveridge
Louisa Revel
Mark Mitchell
Alan Brown
James Woodrow

To return all entries from both tables the Union all command is used:
SELECT FName,LName FROM Users_GB
UNION ALL
SELECT FName,LName FROM Users_FR

UNION ALL combined table

First Name (FName) Last Name (LName)
Peter Smith
Steven Jones
Ruth Mortimer
Kurt Fulmore
Linda Loveridge
Linda Loveridge
Louisa Revel
Mark Mitchell
Alan Brown
James Woodrow