This operator performs an equiality check just like the = operator does, but it will return 1 instead of NULL if both operands are NULL and will return 0 instead of NULL if one operand is NULL.
Sign for NULL safe operator is <=>
Here are some examples showing the usage of the NULL Safe Operator over simple = operator
Examples:
;Simple
SELECT 1=1
; Return 1
;NULL Safe
SELECT 1<=>1
; Return 1
;Simple
SELECT NULL=NULL
; Return NULL
;NULL Safe
SELECT NULL<=>NULL
; Return 1
;Simple
SELECT 1=NULL
; Return NULL
;NULL Safe
SELECT 1<=>NULL
; Return 0
;Simple
SELECT 1=1
; Return 1
;NULL Safe
SELECT 1<=>1
; Return 1
;Simple
SELECT NULL=NULL
; Return NULL
;NULL Safe
SELECT NULL<=>NULL
; Return 1
;Simple
SELECT 1=NULL
; Return NULL
;NULL Safe
SELECT 1<=>NULL
; Return 0
SELECT 1=1
; Return 1
;NULL Safe
SELECT 1<=>1
; Return 1
;Simple
SELECT NULL=NULL
; Return NULL
;NULL Safe
SELECT NULL<=>NULL
; Return 1
;Simple
SELECT 1=NULL
; Return NULL
;NULL Safe
SELECT 1<=>NULL
; Return 0
