Read this SQL tutorial to learn when to use SELECT, JOIN, subselects and UNION to access multiple tables with a single statement. It’s sometimes difficult to know which SQL syntax to use when ...

SQL Server throws a wobbly when one tries to declare/create the same-named temporary table more than once in the same procedure - I guess the query analyser assumes that all temp table creations ...

Here’s the SQL query to select all records from a table: Replace your_table_name with the actual name of the table you want to query. The asterisk (*) is a wildcard that represents all columns ...

The DICTIONARY tables component is specified in the FROM clause of a SELECT statement. DICTIONARY is a reserved libref for use only in PROC SQL. Data from DICTIONARY tables are generated at run time.

I think we can all agree SELECT * in an EXISTS is bad (or can be based on wide tables). I had an interesting case once where I was using a NOT EXISTS to insert data into a large table (~1 billion ...

In SQL Server 2014 there were a number of restrictions on memory-optimized tables: you couldn't alter their structure after they were created; many SQL operators weren't supported (Outer Joins, ...

In an earlier column, I showed how to create a temporal table in SQL Server 2016 or Azure SQL Database. Once you've defined a temporal table, SQL Server automatically keeps a history of all the ...

How to Reindex SQL Tables. The indexes on a the tables of a large database make a huge difference in its performance and utility. Without an index, ...

Basically, you’ll want to enable system-versioning for the source table to a history table which you’ve decided will be temporal. That being the case, you’ll need a couple additional columns of ...

SQL lets you use one command to quickly create a new table containing a subset of records from a larger table while working in Access. Sound complicated? It's not, as Mary Ann Richardson shows us.