Common Table Expressions

Kevin Feasel

2016-01-07

T-SQL

Aaron Bertrand shows us Common Table Expressions:

A CTE is probably best described as a temporary inline view – in spite of its official name, it is not a table, and it is not stored (like a #temp table or @table variable). It operates more like a derived table or subquery, and can only be used for the duration of a single SELECT, UPDATE, INSERT, or DELETE statement (though it can be referenced multiple times within in that statement).

This is a great article on CTEs; give it a read, even if you’re familiar with them.

Related Posts

Matrix Transposition In T-SQL

Phil Factor has some fun transposing a matrix using T-SQL: What I’m doing is simply converting the table into its JSON form, and then using this to create a table using the multi-row VALUES  syntax which paradoxically allows expressions. The expression I’m using is JSON_Value, which allows me do effectively dictate the source within the table, via […]

Read More

Joins And Parentheses

Shane O’Neill walks through different ways of grouping tables in a SQL query: Asker: that’d be awesome if i can inner join two other tables instead of the table mentioned after FROM keyword Me: …wait, what? A: He’s asking t1 left join t12 t1 left join t13 t12 inner join t13 M: em…it’s possible but it’s…iffy […]

Read More

1 Comment

Comments are closed

Categories

January 2016
MTWTFSS
« Dec Feb »
 123
45678910
11121314151617
18192021222324
25262728293031