15.00 - LZDECOMP - Teradata Database

Teradata Database SQL Functions, Operators, Expressions, and Predicates

Product
Teradata Database
Release Number
15.00
Content Type
Programming Reference
Publication ID
B035-1145-015K
Language
English (United States)

LZDECOMP

Purpose  

Uncompresses the Unicode data that was compressed using the LZCOMP function.

Syntax  

where:

 

Syntax element…

Specifies…

TD_SYSFNLIB

the name of the database where the function is located.

compressed_string

Unicode character data that was compressed using the LZCOMP function.

Note: This function takes no arguments when used as part of the COMPRESS USING or DECOMPRESS USING phrases. For more information about the COMPRESS/DECOMPRESS phrase, see SQL Data Types and Literals.

ANSI Compliance

This is a Teradata extension to the ANSI SQL:2011 standard.

Argument Type and Rules

Expressions passed to this function must have a data type of VARBYTE(n), where the maximum supported size (n) is 64000.

The input to this function must be the output result of the LZCOMP function.

If you specify NULL as input, the function returns NULL.

Result Type

The result data type is VARCHAR(32000) CHARACTER SET UNICODE.

Usage Notes

LZDECOMP takes Unicode data that was compressed using the LZCOMP function, uncompresses it, and returns an uncompressed Unicode character string as the result.

See http://zlib.net for information about the decompression algorithm used by LZDECOMP.

Although you can call the function directly, LZDECOMP is normally used with algorithmic compression (ALC) to uncompress table columns previously compressed with LZCOMP.

For more information about ALC, see “COMPRESS and DECOMPRESS Phrases” in SQL Data Types and Literals.

Example

In this example, the Unicode values in the Description column are compressed using the LZCOMP function with ALC. The LZDECOMP function uncompresses the previously compressed values.

   CREATE MULTISET TABLE Pendants
      (ItemNo INTEGER,
       Gem CHAR(10) UPPERCASE CHARACTER SET UNICODE,
       Description VARCHAR(1000) CHARACTER SET UNICODE
          COMPRESS USING TD_SYSFNLIB.LZCOMP
          DECOMPRESS USING TD_SYSFNLIB.LZDECOMP);