String Functions

**Table 1** String functions
No.	MySQL	GaussDB	Difference
1	ASCII()	Supported.	-
2	BIT_LENGTH()	Supported.	-
3	CHAR_LENGTH()	Supported, with differences.	In GaussDB, if the character set is SQL_ASCII, CHAR_LENGTH() returns the number of bytes instead of characters.
4	CHARACTER_LENGTH()	Supported, with differences.	In GaussDB, if the character set is SQL_ASCII, CHARACTER_LENGTH() returns the number of bytes instead of characters.
5	CONCAT()	Supported.	For binary return values, MySQL offers various options (including BINARY, VARBINARY, and BLOB), while GaussDB offers only one—LONGBLOB. For non-binary return values, MySQL offers various options (including CHAR, VARCHAR, and TEXT), while GaussDB only offers TEXT.
6	CONCAT_WS()	Supported.	For binary return values, MySQL offers various options (including BINARY, VARBINARY, and BLOB), while GaussDB offers only one—LONGBLOB. For non-binary return values, MySQL offers various options (including CHAR, VARCHAR, and TEXT), while GaussDB only offers TEXT.
7	HEX()	Supported.	-
8	LENGTH()	Supported.	-
9	LPAD()	Supported, with differences.	The default maximum padding length in MySQL is 1398101, and that in GaussDB is 1048576. The maximum padding length varies depending on the character set. For example, if the character set is GBK, the default maximum padding length in GaussDB is 2097152. If the database character set is SQL_ASCII, unexpected results may occur. For binary return values, MySQL offers various options (including BINARY, VARBINARY, and BLOB), while GaussDB offers only one—LONGBLOB. For non-binary return values, MySQL offers various options (including CHAR, VARCHAR, and TEXT), while GaussDB only offers TEXT.
10	REPEAT()	Supported.	For binary return values, MySQL offers various options (including BINARY, VARBINARY, and BLOB), while GaussDB offers only one—LONGBLOB. For non-binary return values, MySQL offers various options (including CHAR, VARCHAR, and TEXT), while GaussDB only offers TEXT.
11	REPLACE()	Supported.	For binary return values, MySQL offers various options (including BINARY, VARBINARY, and BLOB), while GaussDB offers only one—LONGBLOB. For non-binary return values, MySQL offers various options (including CHAR, VARCHAR, and TEXT), while GaussDB only offers TEXT.
12	RPAD()	Supported, with differences.	The default maximum padding length in MySQL is 1398101, and that in GaussDB is 1048576. The maximum padding length depends on the character set. For example, if the character set is GBK, the default maximum padding length in GaussDB is 2097152. If the database character set is SQL_ASCII, unexpected results may occur. For binary return values, MySQL offers various options (including BINARY, VARBINARY, and BLOB), while GaussDB offers only one—LONGBLOB. For non-binary return values, MySQL offers various options (including CHAR, VARCHAR, and TEXT), while GaussDB only offers TEXT.
13	SPACE()	Supported.	-
14	STRCMP()	Supported, with differences.	If the database character set is SQL_ASCII, unexpected results may occur.
15	FIND_IN_SET()	Supported, with differences.	When characters are specified to be encoded in SQL_ASCII for the database, the server parses byte values 0 to 127 according to the ASCII standard, and byte values 128 to 255 cannot be parsed. If the input and output of the function contain any non-ASCII characters, the database cannot convert or verify them. For binary return values, MySQL offers various options (including BINARY, VARBINARY, and BLOB), while GaussDB offers only one—LONGBLOB. For non-binary return values, MySQL offers various options (including CHAR, VARCHAR, and TEXT), while GaussDB only offers TEXT.
16	LCASE()
17	LEFT()
18	LOWER()
19	LTRIM()
20	REVERSE()
21	RIGHT()
22	RTRIM()
23	SUBSTR()
24	SUBSTRING()
25	SUBSTRING_INDEX()
26	TRIM()
27	UCASE()
28	UPPER()
29	UNHEX()	Supported.	The return value type in MySQL may be BINARY, VARBINARY, BLOB, MEDIUMBLOB, or LONGBLOB, while the return value type in GaussDB is fixed to LONGBLOB.
30	FIELD()	Supported.	-
31	FORMAT()	Supported.	-