Ten Common SQL Programming Mistakes

Without further ado, here is the list:

1. NULLs and the NOT IN predicate
2. Functions on indexed columns in predicates
3. Incorrect subquery column
4. Data type mismatch in predicates
5. Predicate evaluation order
6. Outer joins and placement of predicates
7. Subqueries that return more than one value
8. Use of SELECT *
9. Scalar user-defined functions
10. Overuse of cursors

The examples are presented using SQL Server's Transact-SQL dialect, but most of the concepts are valid in any SQL implementation.


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Happy Programming