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#null

Commands grouped around the same concept, pattern, or recurring problem.

6 commands with this tag Browse related patterns quickly
beginner null-handling MySQL MariaDB SQL Server PostgreSQL SQLite

Check For NULL Values With IS NULL

Use `IS NULL` and `IS NOT NULL` to filter rows based on whether a column has a value.

intermediate joins MySQL MariaDB SQL Server PostgreSQL SQLite

Find Rows With No Matching Related Row

Use a `LEFT JOIN` and filter for `NULL` on the joined table to find missing relationships.

beginner conditional-logic MySQL MariaDB SQL Server PostgreSQL SQLite

Replace NULL Values With COALESCE

Return the first non-null value from a list of expressions.

intermediate null-handling MySQL MariaDB SQL Server PostgreSQL SQLite

Return NULL When Two Values Are Equal With NULLIF

Use `NULLIF` to convert a specific value to `NULL`, most commonly to prevent division-by-zero errors.

beginner aggregation MySQL MariaDB SQL Server PostgreSQL SQLite

Understand COUNT(column) Versus COUNT(*)

`COUNT(column)` skips `NULL` values, while `COUNT(*)` counts every row that made it into the result set.

intermediate null-handling MySQL MariaDB SQL Server PostgreSQL SQLite

Use NOT IN Safely When NULLs Are Possible

Filter `NULL` values out of the right side before using `NOT IN`, or the predicate can exclude everything.