COMPRESS (Transact-SQL)

Artikel
05/23/2023

Applies to: SQL Server 2016 (13.x) and later Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics SQL analytics endpoint in Microsoft Fabric Warehouse in Microsoft Fabric

This function compresses the input expression, using the Gzip algorithm. The function returns a byte array of type varbinary(max).

Transact-SQL syntax conventions

Syntax

COMPRESS ( expression )

Arguments

expression

An expression of one of the following data types:

binary(n)
char(n)
nchar(n)
nvarchar(max)
nvarchar(n)
varbinary(max)
varbinary(n)
varchar(max)
varchar(n)

For more information, see Expressions (Transact-SQL).

Return type

varbinary(max), representing the compressed content of the input.

Remarks

Compressed data can't be indexed.

The COMPRESS function compresses the input expression data. You must invoke this function for each data section to compress. For more information about automatic data compression during storage at the row or page level, see Data Compression.

Examples

A. Compress data during table insert

This example shows how to compress data inserted into a table:

INSERT INTO player (
    name,
    surname,
    info
    )
VALUES (
    N'Ovidiu',
    N'Cracium',
    COMPRESS(N'{"sport":"Tennis","age": 28,"rank":1,"points":15258, turn":17}')
    );

INSERT INTO player (
    name,
    surname,
    info
    )
VALUES (
    N'Michael',
    N'Raheem',
    COMPRESS(@info)
    );

B. Archive compressed version of deleted rows

This statement first deletes old player records from the player table. To save space, it then stores the records in the inactivePlayer table, in a compressed format.

DELETE
FROM player
OUTPUT deleted.id,
    deleted.name,
    deleted.surname,
    deleted.datemodifier,
    COMPRESS(deleted.info)
INTO dbo.inactivePlayers
WHERE datemodified < @startOfYear;

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