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.

    
         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

    
         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

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

Output

    
         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.

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

Output

    
         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");