What is DECODE function?

What is DECODE function?

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The DECODE function decodes a column value or an expression and compares it with each specified search value, one by one. If the expression matches a search value, a result value corresponding to the matching search value is returned. If no match is found, a default result value, if included, is returned. However, if no default value is included, a NULL value is returned. The DECODE function is one of the few single-row functions that directly deal with NULL values. It can compare two NULL values and can return a NULL value.

Syntax:

DECODE (ColumnExpression, search, result[, search, result, ...] [, default] )

ColumnExpression, search, and result can be of the CHAR, VARCHAR2, NCHAR, or NVARCHAR2 datatype.

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