Returns the first of its arguments that is not null.
Returns null if all arguments are null.
This function is often used to substitute a default value for null values.
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coalesce(expression1[, ..., expression_n])
Arguments
expression1, expression_n:
Expression to use if previous expressions are null.
Can be a constant, column, or function, and any combination of arithmetic operators.
Pass as many expression arguments as necessary.
Returns null if expression1 equals expression2; otherwise it returns expression1.
This can be used to perform the inverse operation of coalesce.
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nullif(expression1, expression2)
Arguments
expression1: Expression to compare and return if equal to expression2.
Can be a constant, column, or function, and any combination of arithmetic operators.
expression2: Expression to compare to expression1.
Can be a constant, column, or function, and any combination of arithmetic operators.