COALESCE replaces a NULL with a fallback value
When a cell holds NULL, you often want to show something friendlier than nothing. COALESCE reads its values left to right and returns the first one that is not NULL. So if a student's nickname is NULL, it falls back to their name instead.
A tiny example
In plain English: Show me each student's nickname, or their name when there is no nickname.
SELECT COALESCE(nickname, name) AS label
FROM students;What comes back
| label |
|---|
| Mimi |
| Otto |
Mia has the nickname Mimi, so that wins; Otto's nickname is NULL, so it fell back to Otto.
Related SQL lessons
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