Month: January 2019

ORDER BY CASE

In TSQL I recently discovered how to use the CASE command in the ORDER BY clause to sort results in custom ways.

For example, to order countries with the UK and USA at the top then the rest alphabetically would in the past have caused me to either generate a calculated ‘CountrySort’ column or UNION two queries.

Now I can do this …

ORDER BY CASE
		WHEN countryid = 1 THEN 'AAA'
		WHEN countryid = 23 THEN 'AAB'
		ELSE countryname END

Which translates as …

‘Order by countryname
having first replaced the countryname with ‘AAA’ where the countryid is 1
and ‘AAB’ where its 23′.

Here are the results (including countryid for clarity)…

countrysort

Column Max Length

From my “Spreadsheet sizer” script, this one helped me move sensibly away from pesky varchar(max) columns.

-- ColumnMaxLength.sql

DECLARE @TableName VARCHAR(255) = 'customers' --<< input
DECLARE @SchemaName VARCHAR(255) = 'dbo' 
DECLARE @sqlcmd varchar(max) 

select @sqlcmd = stuff((SELECT ' union all
select ' 
+ QUOTENAME(table_schema,'''') + ' [Schema], ' 
+ QUOTENAME(TABLE_NAME,'''') + ' [Table], ' 
+ quotename(column_name,'''') + ' [Column],
max(datalength(' + quotename(column_name) + ')) MaxLength 
from ' + quotename(table_schema) + '.' + quotename(table_name)
from information_schema.columns
where 1=1
AND table_name =  @TableName
AND table_schema = @SchemaName
order by column_name
for xml path(''),type).value('.','varchar(max)'),1,11,'')

exec(@sqlcmd)

Comparing Stored-Procedures

Had a bit of a problem today with the re-write project.

I had been checking new stored-procedures in the DEV database, and (if good) pasting them into the WEB database.

The issue was that some DEV stored-procedures that I had already checked-in to WEB had been modified again.

Rather than trying to enforce version-control (mmm), or download Redgate’s SQL Compare, I modified my ‘Whats New” routine to compare the modify-dates between the DEV and WEB databases.

-- CompareSP.sql

SELECT [dev].[type_desc],
       (SELECT [name] FROM [companydev].[sys].[schemas] WHERE [schema_id] = [dev].[schema_id]) [schema],
       CASE [dev].[parent_object_id]
           WHEN '0' THEN [dev].[name]
           ELSE OBJECT_NAME([dev].[parent_object_id]) + '.' + [dev].[name]
       END [object_name],
       [dev].[create_date],
       [dev].[modify_date], -- or create-date if there isn't one
	   '' v,
	   [web].[modify_date] web_modify_date , 
	   DATEDIFF(MINUTE, [dev].[modify_date], [web].[modify_date]) mod_diff
FROM [companydev].[sys].[objects] dev
JOIN [companyweb].[sys].[objects] web
  ON [dev].[name] = [web].[name]
WHERE [dev].[is_ms_shipped] = 0 -- exclude system-objects
AND [dev].[type] = 'P' -- just stored-procedures
--AND [dev].[modify_date] > '21 nov 2018'
ORDER BY [dev].[modify_date] DESC;

Adding a NOT NULL column to an existing table

-- AddingNotNullColumnToExistingTable.sql

-- 1. Add new column to the old table, as NULL for now

	ALTER TABLE [dbo].[TableName] 
	ADD [ColumnName] INT NULL

-- 2. Set the default to zero for new rows

	ALTER TABLE [dbo].[TableName] 
	ADD CONSTRAINT [DF_TableName_ColumnName] 
	DEFAULT(0) FOR [ColumnName]

-- 3. Change all existing null values to zeros

	UPDATE [dbo].[TableName] 
	SET [ColumnName] = 0 
	WHERE [ColumnName] IS NULL

-- 4. Change column from NULL to NOT NULL

	ALTER TABLE [dbo].[TableName] 
	ALTER COLUMN [ColumnName] INT NOT NULL

-- Undo (while testing)

	ALTER TABLE [dbo].[TableName] 
	DROP CONSTRAINT [DF_TableName_ColumnName]

	ALTER TABLE [dbo].[TableName] 
	DROP COLUMN [ColumnName]