ISNULL

As a function

ISNULL( expression )

As an operator

expression IS [ NOT ] NULL

Returns TRUE if expression is NULL, otherwise returns FALSE.

expression IS NOT NULL returns the opposite result.

Argument types:

Return type: Boolean

[sales]	ISNULL([sales])	[sales] IS NULL	[sales] IS NOT NULL
`432.40`	`False`	`False`	`True`
`77.00`	`False`	`False`	`True`
`12000.00`	`False`	`False`	`True`
`NULL`	`True`	`True`	`False`
`34.25`	`False`	`False`	`True`
`128.00`	`False`	`False`	`True`
`0.00`	`False`	`False`	`True`
`NULL`	`True`	`True`	`False`

ClickHouse 19.13, Microsoft SQL Server 2017 (14.0), MySQL 5.6, PostgreSQL 9.3.