Help Center/ Data Warehouse Service/ Tool Guide/ DSC/ MySQL Syntax Migrating/ Data Types/ String Types
Updated on 2025-04-10 GMT+08:00
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String Types

Overview

MySQL interprets length specifications in character column definitions in character units. This applies to the CHAR, VARCHAR, and TEXT types. DSC supports the following type conversions:

Type Mapping

Table 1 String type mapping

MySQL String Type

MySQL INPUT

GaussDB(DWS) OUTPUT

CHAR

CHAR[(0)]

CHAR[(n)]

CHAR[(1)]

CHAR[(4n)]

CHARACTER

CHARACTER[(0)]

CHARACTER[(n)]

CHAR[(1)]

CHAR[(4n)]

NCHAR

NCHAR[(0)]

NCHAR[(n)]

CHAR[(1)]

CHAR[(4n)]

LONGTEXT

LONGTEXT

TEXT

MEDIUMTEXT

MEDIUMTEXT

TEXT

TEXT

TEXT

TEXT

TINYTEXT

TINYTEXT

TEXT

VARCHAR

VARCHAR[(0)]

VARCHAR[(n)]

VARCHAR[(1)]

VARCHAR[(4n)]

NVARCHAR

NVARCHAR[(0)]

NVARCHAR[(n)]

VARCHAR[(1)]

VARCHAR[(4n)]

CHARACTE VARYING

CHARACTE VARYING

VARCHAR
  • During CHAR/CHARACTER/NCHAR conversion, if the precision is less than or equal to 0, it is converted to CHAR(1). If the precision is greater than 0, it is converted to a precision level four times that of the CHAR type.
  • During VARCHAR/NVARCHAR conversion, if the precision is less than or equal to 0, it is converted to VARCHAR(1). If the precision is greater than 0, it is converted to a precision four times that of the VARCHAR type.

Input: CHAR

In MySQL, the size of a CHAR column is set to a fixed length specified at table creation, ranging from 0 to 255. Stored CHAR values are right-padded with spaces to meet this specified length.

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CREATE TABLE IF NOT EXISTS `runoob_dataType_test`(
   `dataType_1` CHAR NOT NULL,
   `dataType_2` CHAR(0) NOT NULL,
   `dataType_3` CHAR(255) NOT NULL
);

Output

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CREATE TABLE IF NOT EXISTS "public"."runoob_datatype_test"
(
  "datatype_1" CHAR NOT NULL,
  "datatype_2" CHAR(1) NOT NULL,
  "datatype_3" CHAR(1020) NOT NULL
)
  WITH ( ORIENTATION = ROW, COMPRESSION = NO )
  NOCOMPRESS
  DISTRIBUTE BY HASH ("datatype_1");

Input: [LONG|MEDIUM|TINY]TEXT

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CREATE TABLE IF NOT EXISTS `runoob_dataType_test`(
    `dataType_1` LONGTEXT,
    `dataType_2` MEDIUMTEXT,
    `dataType_3` TEXT,
    `dataType_4` TINYTEXT
);

Output

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CREATE TABLE IF NOT EXISTS "public"."runoob_datatype_test"
(
  "datatype_1" TEXT,
  "datatype_2" TEXT,
  "datatype_3" TEXT,
  "datatype_4" TEXT
)
  WITH ( ORIENTATION = ROW, COMPRESSION = NO )
  NOCOMPRESS
  DISTRIBUTE BY HASH ("datatype_1");

Input: VARCHAR

In MySQL, values in VARCHAR columns are variable-length strings. The length can be any value from 0 to 65,535.

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CREATE TABLE IF NOT EXISTS `runoob_dataType_test`(
    `dataType_1` VARCHAR(0),
    `dataType_2` VARCHAR(1845)
);

Output

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CREATE TABLE IF NOT EXISTS "public"."runoob_datatype_test"
(
  "datatype_1" VARCHAR(1),
  "datatype_2" VARCHAR(7380)
)
  WITH ( ORIENTATION = ROW, COMPRESSION = NO )
  NOCOMPRESS
  DISTRIBUTE BY HASH ("datatype_1");
Parent topic: Data Types