Tag: SQL

Just one of those things you may not know existed - the ROLLUP clause. It's very useful for totaling. Are you used to doing something like this? SELECT customer, sum(sales) from table UNION SELECT 'Total', sum(sales) from table The problem here is that on larger datasets, this can really be a pain in terms of performance. ROLLUP can be extremely quick, but the syntax may not be straight forward. Here's an example of summing sales in AdventureWorks2017 with a Grand Total. USE AdventureWorks2017 SELECT SalesOrderID, sum(LineTotal) FROM Sales.SalesOrderDetail where SalesOrderID in ( '43659', '43660', '43661', '43662', '43663' ) GROUP BY SalesOrderID WITH ROLLUP Notice I've added a WITH ROLLUP at the end of my GROUP BY. This creates the grand total. However, I'm left with a NULL for the SalesOrderID. To solve this I wouldn't want to use a coalesce, because a NULL might be valid elsewhere. Instead we should use the GROUPING function. USE AdventureWorks2017 SELECT CASE WHEN GROUPING(SalesOrderID) = 1 THEN 'Total' ELSE cast(SalesOrderID as nvarchar(10)) END as SalesOrderID, sum(LineTotal) FROM Sales.SalesOrderDetail where SalesOrderID in ( '43659', '43660', '43661', '43662', '43663' ) GROUP BY SalesOrderID WITH ROLLUP You can extend this even further...

A nifty little bit of code I've used for years and years, very useful if you don't have a third party add-on installed... USE AdventureWorks2017 SELECT * FROM ( SELECT t.name AS name, 'table' as type, SCHEMA_NAME(schema_id) AS schema_name, c.name AS column_name FROM sys.tables AS t INNER JOIN sys.columns c ON t.OBJECT_ID = c.OBJECT_ID WHERE c.name LIKE '%Employee%' UNION SELECT v.name AS name, 'view' as type, SCHEMA_NAME(schema_id) AS schema_name, c.name AS column_name FROM sys.views AS v INNER JOIN sys.columns c ON v.OBJECT_ID = c.OBJECT_ID WHERE c.name LIKE '%Employee%' ) a ORDER BY schema_name, name ...

One problem I've had recently is a SQL Server instance in which the views were constantly cached and needed to be refreshed. Normally to do this you would run the build in procedure: exec sp_refreshview MyView However - I had the need to run this on all my views daily, and we constantly had new views. You can use the stored proc below to simply loop all the views and run as needed. create procedure usp_refreshview as declare @sqlcmd nvarchar(max) = '' select @sqlcmd = @sqlcmd + 'exec sp_refreshview ' + '''' + name + '''; ' from sys.objects as so where so.type = 'V' print @sqlcmd if len(@sqlcmd) > 0 exec(@sqlcmd) To run, simply exec: exec usp_refreshview ...

A useful bit of syntax in the case that you end up with multiple levels of granularity in a dataset, and you want to collapse it back down. One solution would be to turn your rows into columns (pivoting), or put your row values into a single column separated by commas (or pipes, etc.). Below I'm using the AdventureWorks2017 database to show how to do the latter. SELECT [CountryRegionCode] ,StateProvinceCode FROM [AdventureWorks2017].[Person].[StateProvince] Here it produces a gigantic list of countries with associated state/provinces. So let's collapse that down... SELECT outerQ.[CountryRegionCode], STUFF(( SELECT DISTINCT ',' + subQ.StateProvinceCode FROM [AdventureWorks2017].[Person].[StateProvince] subQ WHERE outerQ.CountryRegionCode = subQ.CountryRegionCode FOR XML PATH('') ), 1, 1, '' ) as LastNameList FROM [AdventureWorks2017].[Person].[StateProvince] outerQ GROUP BY outerQ.[CountryRegionCode]; ...

The bane of my existence, blank values that should be NULL in a database. This happens frequently when importing Excel/Flat files particularly within SQL Server. Running hundreds of UPDATE statements isn't fun, so I use a Stored Procedure with a CURSOR to take care of it. CREATE PROCEDURE [dbo].[usp_getRidOfTableBlanks](@tableName nvarchar(50)) AS DECLARE @colName varchar(255) DECLARE @sql varchar(4000) DECLARE Table_Cursor CURSOR FOR select COLUMN_NAME from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME=@tableName OPEN Table_Cursor; FETCH NEXT FROM Table_Cursor INTO @colName WHILE @@FETCH_STATUS = 0 BEGIN set @sql = 'UPDATE ' + @tableName + ' SET [' + @colName + '] = NULL WHERE [' + @colName + '] = '''';'; ...