SQL · NULL Handling & Data Types

COALESCE vs NULLIF

Easysql-27

coalescenullifnull

Question

What is the difference between COALESCE and NULLIF?

COALESCE() returns the first non-NULL value.

COALESCE(phone, email, 'No contact')

means:

> Use phone; if NULL, use email; if that is NULL, use "No contact".

NULLIF(a,b) returns NULL when a = b.

NULLIF(quantity, 0)

is useful for avoiding division by zero:

sales / NULLIF(quantity, 0)

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