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¶
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 |
Note
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");