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ADD COLUMNADD INDEXADMINADMIN CANCEL DDLADMIN CHECKSUM TABLEADMIN CHECK [TABLE|INDEX]ADMIN SHOW DDL [JOBS|QUERIES]ALTER DATABASEALTER TABLEALTER USERANALYZE TABLEBEGINCHANGE COLUMNCOMMITCREATE DATABASECREATE INDEXCREATE TABLE LIKECREATE TABLECREATE USERDEALLOCATEDELETEDESCDESCRIBEDODROP COLUMNDROP DATABASEDROP INDEXDROP TABLEDROP USEREXECUTEEXPLAIN ANALYZEEXPLAINFLUSH PRIVILEGESFLUSH STATUSFLUSH TABLESGRANT <privileges>INSERTKILL [TIDB]LOAD DATALOAD STATSMODIFY COLUMNPREPARERENAME INDEXRENAME TABLEREPLACEREVOKE <privileges>ROLLBACKSELECTSET [NAMES|CHARACTER SET]SET PASSWORDSET TRANSACTIONSET [GLOBAL|SESSION] <variable>SHOW CHARACTER SETSHOW COLLATIONSHOW [FULL] COLUMNS FROMSHOW CREATE TABLESHOW DATABASESSHOW ENGINESSHOW ERRORSSHOW [FULL] FIELDS FROMSHOW GRANTSSHOW INDEXES [FROM|IN]SHOW INDEX [FROM|IN]SHOW KEYS [FROM|IN]SHOW PRIVILEGESSHOW [FULL] PROCESSSLISTSHOW SCHEMASSHOW STATUSSHOW [FULL] TABLESSHOW TABLE STATUSSHOW [GLOBAL|SESSION] VARIABLESSHOW WARNINGSSTART TRANSACTIONTRACETRUNCATEUPDATEUSE
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- Glossary
Character Set Support
A character set is a set of symbols and encodings. A collation is a set of rules for comparing characters in a character set.
Currently, TiDB supports the following character sets:
mysql> SHOW CHARACTER SET;
+---------|---------------|-------------------|--------+
| Charset | Description | Default collation | Maxlen |
+---------|---------------|-------------------|--------+
| utf8 | UTF-8 Unicode | utf8_bin | 3 |
| utf8mb4 | UTF-8 Unicode | utf8mb4_bin | 4 |
| ascii | US ASCII | ascii_bin | 1 |
| latin1 | Latin1 | latin1_bin | 1 |
| binary | binary | binary | 1 |
+---------|---------------|-------------------|--------+
5 rows in set (0.00 sec)Note:
In TiDB, utf8 is treated as utf8mb4.
Collation support
TiDB only supports binary collations. This means that unlike MySQL, in TiDB string comparisons are both case sensitive and accent sensitive:
mysql> SELECT * FROM information_schema.collations;
+--------------------------+--------------------+------+------------+-------------+---------+
| COLLATION_NAME | CHARACTER_SET_NAME | ID | IS_DEFAULT | IS_COMPILED | SORTLEN |
+--------------------------+--------------------+------+------------+-------------+---------+
| big5_chinese_ci | big5 | 1 | Yes | Yes | 1 |
| latin2_czech_cs | latin2 | 2 | | Yes | 1 |
| dec8_swedish_ci | dec8 | 3 | Yes | Yes | 1 |
| cp850_general_ci | cp850 | 4 | Yes | Yes | 1 |
| latin1_german1_ci | latin1 | 5 | | Yes | 1 |
| hp8_english_ci | hp8 | 6 | Yes | Yes | 1 |
| koi8r_general_ci | koi8r | 7 | Yes | Yes | 1 |
| latin1_swedish_ci | latin1 | 8 | Yes | Yes | 1 |
| latin2_general_ci | latin2 | 9 | Yes | Yes | 1 |
| swe7_swedish_ci | swe7 | 10 | Yes | Yes | 1 |
| ascii_general_ci | ascii | 11 | Yes | Yes | 1 |
| ujis_japanese_ci | ujis | 12 | Yes | Yes | 1 |
| sjis_japanese_ci | sjis | 13 | Yes | Yes | 1 |
| cp1251_bulgarian_ci | cp1251 | 14 | | Yes | 1 |
| latin1_danish_ci | latin1 | 15 | | Yes | 1 |
| hebrew_general_ci | hebrew | 16 | Yes | Yes | 1 |
| tis620_thai_ci | tis620 | 18 | Yes | Yes | 1 |
| euckr_korean_ci | euckr | 19 | Yes | Yes | 1 |
| latin7_estonian_cs | latin7 | 20 | | Yes | 1 |
| latin2_hungarian_ci | latin2 | 21 | | Yes | 1 |
| koi8u_general_ci | koi8u | 22 | Yes | Yes | 1 |
| cp1251_ukrainian_ci | cp1251 | 23 | | Yes | 1 |
| gb2312_chinese_ci | gb2312 | 24 | Yes | Yes | 1 |
| greek_general_ci | greek | 25 | Yes | Yes | 1 |
| cp1250_general_ci | cp1250 | 26 | Yes | Yes | 1 |
| latin2_croatian_ci | latin2 | 27 | | Yes | 1 |
| gbk_chinese_ci | gbk | 28 | Yes | Yes | 1 |
| cp1257_lithuanian_ci | cp1257 | 29 | | Yes | 1 |
| latin5_turkish_ci | latin5 | 30 | Yes | Yes | 1 |
| latin1_german2_ci | latin1 | 31 | | Yes | 1 |
| armscii8_general_ci | armscii8 | 32 | Yes | Yes | 1 |
| utf8_general_ci | utf8 | 33 | Yes | Yes | 1 |
| cp1250_czech_cs | cp1250 | 34 | | Yes | 1 |
| ucs2_general_ci | ucs2 | 35 | Yes | Yes | 1 |
| cp866_general_ci | cp866 | 36 | Yes | Yes | 1 |
| keybcs2_general_ci | keybcs2 | 37 | Yes | Yes | 1 |
| macce_general_ci | macce | 38 | Yes | Yes | 1 |
| macroman_general_ci | macroman | 39 | Yes | Yes | 1 |
| cp852_general_ci | cp852 | 40 | Yes | Yes | 1 |
| latin7_general_ci | latin7 | 41 | Yes | Yes | 1 |
| latin7_general_cs | latin7 | 42 | | Yes | 1 |
| macce_bin | macce | 43 | | Yes | 1 |
| cp1250_croatian_ci | cp1250 | 44 | | Yes | 1 |
| utf8mb4_general_ci | utf8mb4 | 45 | Yes | Yes | 1 |
| utf8mb4_bin | utf8mb4 | 46 | | Yes | 1 |
| latin1_bin | latin1 | 47 | | Yes | 1 |
| latin1_general_ci | latin1 | 48 | | Yes | 1 |
| latin1_general_cs | latin1 | 49 | | Yes | 1 |
| cp1251_bin | cp1251 | 50 | | Yes | 1 |
| cp1251_general_ci | cp1251 | 51 | Yes | Yes | 1 |
| cp1251_general_cs | cp1251 | 52 | | Yes | 1 |
| macroman_bin | macroman | 53 | | Yes | 1 |
| utf16_general_ci | utf16 | 54 | Yes | Yes | 1 |
| utf16_bin | utf16 | 55 | | Yes | 1 |
| utf16le_general_ci | utf16le | 56 | Yes | Yes | 1 |
| cp1256_general_ci | cp1256 | 57 | Yes | Yes | 1 |
| cp1257_bin | cp1257 | 58 | | Yes | 1 |
| cp1257_general_ci | cp1257 | 59 | Yes | Yes | 1 |
| utf32_general_ci | utf32 | 60 | Yes | Yes | 1 |
| utf32_bin | utf32 | 61 | | Yes | 1 |
| utf16le_bin | utf16le | 62 | | Yes | 1 |
| binary | binary | 63 | Yes | Yes | 1 |
| armscii8_bin | armscii8 | 64 | | Yes | 1 |
| ascii_bin | ascii | 65 | | Yes | 1 |
| cp1250_bin | cp1250 | 66 | | Yes | 1 |
| cp1256_bin | cp1256 | 67 | | Yes | 1 |
| cp866_bin | cp866 | 68 | | Yes | 1 |
| dec8_bin | dec8 | 69 | | Yes | 1 |
| greek_bin | greek | 70 | | Yes | 1 |
| hebrew_bin | hebrew | 71 | | Yes | 1 |
| hp8_bin | hp8 | 72 | | Yes | 1 |
| keybcs2_bin | keybcs2 | 73 | | Yes | 1 |
| koi8r_bin | koi8r | 74 | | Yes | 1 |
| koi8u_bin | koi8u | 75 | | Yes | 1 |
| latin2_bin | latin2 | 77 | | Yes | 1 |
| latin5_bin | latin5 | 78 | | Yes | 1 |
| latin7_bin | latin7 | 79 | | Yes | 1 |
| cp850_bin | cp850 | 80 | | Yes | 1 |
| cp852_bin | cp852 | 81 | | Yes | 1 |
| swe7_bin | swe7 | 82 | | Yes | 1 |
| utf8_bin | utf8 | 83 | | Yes | 1 |
| big5_bin | big5 | 84 | | Yes | 1 |
| euckr_bin | euckr | 85 | | Yes | 1 |
| gb2312_bin | gb2312 | 86 | | Yes | 1 |
| gbk_bin | gbk | 87 | | Yes | 1 |
| sjis_bin | sjis | 88 | | Yes | 1 |
| tis620_bin | tis620 | 89 | | Yes | 1 |
| ucs2_bin | ucs2 | 90 | | Yes | 1 |
| ujis_bin | ujis | 91 | | Yes | 1 |
| geostd8_general_ci | geostd8 | 92 | Yes | Yes | 1 |
| geostd8_bin | geostd8 | 93 | | Yes | 1 |
| latin1_spanish_ci | latin1 | 94 | | Yes | 1 |
| cp932_japanese_ci | cp932 | 95 | Yes | Yes | 1 |
| cp932_bin | cp932 | 96 | | Yes | 1 |
| eucjpms_japanese_ci | eucjpms | 97 | Yes | Yes | 1 |
| eucjpms_bin | eucjpms | 98 | | Yes | 1 |
| cp1250_polish_ci | cp1250 | 99 | | Yes | 1 |
| utf16_unicode_ci | utf16 | 101 | | Yes | 1 |
| utf16_icelandic_ci | utf16 | 102 | | Yes | 1 |
| utf16_latvian_ci | utf16 | 103 | | Yes | 1 |
| utf16_romanian_ci | utf16 | 104 | | Yes | 1 |
| utf16_slovenian_ci | utf16 | 105 | | Yes | 1 |
| utf16_polish_ci | utf16 | 106 | | Yes | 1 |
| utf16_estonian_ci | utf16 | 107 | | Yes | 1 |
| utf16_spanish_ci | utf16 | 108 | | Yes | 1 |
| utf16_swedish_ci | utf16 | 109 | | Yes | 1 |
| utf16_turkish_ci | utf16 | 110 | | Yes | 1 |
| utf16_czech_ci | utf16 | 111 | | Yes | 1 |
| utf16_danish_ci | utf16 | 112 | | Yes | 1 |
| utf16_lithuanian_ci | utf16 | 113 | | Yes | 1 |
| utf16_slovak_ci | utf16 | 114 | | Yes | 1 |
| utf16_spanish2_ci | utf16 | 115 | | Yes | 1 |
| utf16_roman_ci | utf16 | 116 | | Yes | 1 |
| utf16_persian_ci | utf16 | 117 | | Yes | 1 |
| utf16_esperanto_ci | utf16 | 118 | | Yes | 1 |
| utf16_hungarian_ci | utf16 | 119 | | Yes | 1 |
| utf16_sinhala_ci | utf16 | 120 | | Yes | 1 |
| utf16_german2_ci | utf16 | 121 | | Yes | 1 |
| utf16_croatian_ci | utf16 | 122 | | Yes | 1 |
| utf16_unicode_520_ci | utf16 | 123 | | Yes | 1 |
| utf16_vietnamese_ci | utf16 | 124 | | Yes | 1 |
| ucs2_unicode_ci | ucs2 | 128 | | Yes | 1 |
| ucs2_icelandic_ci | ucs2 | 129 | | Yes | 1 |
| ucs2_latvian_ci | ucs2 | 130 | | Yes | 1 |
| ucs2_romanian_ci | ucs2 | 131 | | Yes | 1 |
| ucs2_slovenian_ci | ucs2 | 132 | | Yes | 1 |
| ucs2_polish_ci | ucs2 | 133 | | Yes | 1 |
| ucs2_estonian_ci | ucs2 | 134 | | Yes | 1 |
| ucs2_spanish_ci | ucs2 | 135 | | Yes | 1 |
| ucs2_swedish_ci | ucs2 | 136 | | Yes | 1 |
| ucs2_turkish_ci | ucs2 | 137 | | Yes | 1 |
| ucs2_czech_ci | ucs2 | 138 | | Yes | 1 |
| ucs2_danish_ci | ucs2 | 139 | | Yes | 1 |
| ucs2_lithuanian_ci | ucs2 | 140 | | Yes | 1 |
| ucs2_slovak_ci | ucs2 | 141 | | Yes | 1 |
| ucs2_spanish2_ci | ucs2 | 142 | | Yes | 1 |
| ucs2_roman_ci | ucs2 | 143 | | Yes | 1 |
| ucs2_persian_ci | ucs2 | 144 | | Yes | 1 |
| ucs2_esperanto_ci | ucs2 | 145 | | Yes | 1 |
| ucs2_hungarian_ci | ucs2 | 146 | | Yes | 1 |
| ucs2_sinhala_ci | ucs2 | 147 | | Yes | 1 |
| ucs2_german2_ci | ucs2 | 148 | | Yes | 1 |
| ucs2_croatian_ci | ucs2 | 149 | | Yes | 1 |
| ucs2_unicode_520_ci | ucs2 | 150 | | Yes | 1 |
| ucs2_vietnamese_ci | ucs2 | 151 | | Yes | 1 |
| ucs2_general_mysql500_ci | ucs2 | 159 | | Yes | 1 |
| utf32_unicode_ci | utf32 | 160 | | Yes | 1 |
| utf32_icelandic_ci | utf32 | 161 | | Yes | 1 |
| utf32_latvian_ci | utf32 | 162 | | Yes | 1 |
| utf32_romanian_ci | utf32 | 163 | | Yes | 1 |
| utf32_slovenian_ci | utf32 | 164 | | Yes | 1 |
| utf32_polish_ci | utf32 | 165 | | Yes | 1 |
| utf32_estonian_ci | utf32 | 166 | | Yes | 1 |
| utf32_spanish_ci | utf32 | 167 | | Yes | 1 |
| utf32_swedish_ci | utf32 | 168 | | Yes | 1 |
| utf32_turkish_ci | utf32 | 169 | | Yes | 1 |
| utf32_czech_ci | utf32 | 170 | | Yes | 1 |
| utf32_danish_ci | utf32 | 171 | | Yes | 1 |
| utf32_lithuanian_ci | utf32 | 172 | | Yes | 1 |
| utf32_slovak_ci | utf32 | 173 | | Yes | 1 |
| utf32_spanish2_ci | utf32 | 174 | | Yes | 1 |
| utf32_roman_ci | utf32 | 175 | | Yes | 1 |
| utf32_persian_ci | utf32 | 176 | | Yes | 1 |
| utf32_esperanto_ci | utf32 | 177 | | Yes | 1 |
| utf32_hungarian_ci | utf32 | 178 | | Yes | 1 |
| utf32_sinhala_ci | utf32 | 179 | | Yes | 1 |
| utf32_german2_ci | utf32 | 180 | | Yes | 1 |
| utf32_croatian_ci | utf32 | 181 | | Yes | 1 |
| utf32_unicode_520_ci | utf32 | 182 | | Yes | 1 |
| utf32_vietnamese_ci | utf32 | 183 | | Yes | 1 |
| utf8_unicode_ci | utf8 | 192 | | Yes | 1 |
| utf8_icelandic_ci | utf8 | 193 | | Yes | 1 |
| utf8_latvian_ci | utf8 | 194 | | Yes | 1 |
| utf8_romanian_ci | utf8 | 195 | | Yes | 1 |
| utf8_slovenian_ci | utf8 | 196 | | Yes | 1 |
| utf8_polish_ci | utf8 | 197 | | Yes | 1 |
| utf8_estonian_ci | utf8 | 198 | | Yes | 1 |
| utf8_spanish_ci | utf8 | 199 | | Yes | 1 |
| utf8_swedish_ci | utf8 | 200 | | Yes | 1 |
| utf8_turkish_ci | utf8 | 201 | | Yes | 1 |
| utf8_czech_ci | utf8 | 202 | | Yes | 1 |
| utf8_danish_ci | utf8 | 203 | | Yes | 1 |
| utf8_lithuanian_ci | utf8 | 204 | | Yes | 1 |
| utf8_slovak_ci | utf8 | 205 | | Yes | 1 |
| utf8_spanish2_ci | utf8 | 206 | | Yes | 1 |
| utf8_roman_ci | utf8 | 207 | | Yes | 1 |
| utf8_persian_ci | utf8 | 208 | | Yes | 1 |
| utf8_esperanto_ci | utf8 | 209 | | Yes | 1 |
| utf8_hungarian_ci | utf8 | 210 | | Yes | 1 |
| utf8_sinhala_ci | utf8 | 211 | | Yes | 1 |
| utf8_german2_ci | utf8 | 212 | | Yes | 1 |
| utf8_croatian_ci | utf8 | 213 | | Yes | 1 |
| utf8_unicode_520_ci | utf8 | 214 | | Yes | 1 |
| utf8_vietnamese_ci | utf8 | 215 | | Yes | 1 |
| utf8_general_mysql500_ci | utf8 | 223 | | Yes | 1 |
| utf8mb4_unicode_ci | utf8mb4 | 224 | | Yes | 1 |
| utf8mb4_icelandic_ci | utf8mb4 | 225 | | Yes | 1 |
| utf8mb4_latvian_ci | utf8mb4 | 226 | | Yes | 1 |
| utf8mb4_romanian_ci | utf8mb4 | 227 | | Yes | 1 |
| utf8mb4_slovenian_ci | utf8mb4 | 228 | | Yes | 1 |
| utf8mb4_polish_ci | utf8mb4 | 229 | | Yes | 1 |
| utf8mb4_estonian_ci | utf8mb4 | 230 | | Yes | 1 |
| utf8mb4_spanish_ci | utf8mb4 | 231 | | Yes | 1 |
| utf8mb4_swedish_ci | utf8mb4 | 232 | | Yes | 1 |
| utf8mb4_turkish_ci | utf8mb4 | 233 | | Yes | 1 |
| utf8mb4_czech_ci | utf8mb4 | 234 | | Yes | 1 |
| utf8mb4_danish_ci | utf8mb4 | 235 | | Yes | 1 |
| utf8mb4_lithuanian_ci | utf8mb4 | 236 | | Yes | 1 |
| utf8mb4_slovak_ci | utf8mb4 | 237 | | Yes | 1 |
| utf8mb4_spanish2_ci | utf8mb4 | 238 | | Yes | 1 |
| utf8mb4_roman_ci | utf8mb4 | 239 | | Yes | 1 |
| utf8mb4_persian_ci | utf8mb4 | 240 | | Yes | 1 |
| utf8mb4_esperanto_ci | utf8mb4 | 241 | | Yes | 1 |
| utf8mb4_hungarian_ci | utf8mb4 | 242 | | Yes | 1 |
| utf8mb4_sinhala_ci | utf8mb4 | 243 | | Yes | 1 |
| utf8mb4_german2_ci | utf8mb4 | 244 | | Yes | 1 |
| utf8mb4_croatian_ci | utf8mb4 | 245 | | Yes | 1 |
| utf8mb4_unicode_520_ci | utf8mb4 | 246 | | Yes | 1 |
| utf8mb4_vietnamese_ci | utf8mb4 | 247 | | Yes | 1 |
| utf8mb4_0900_ai_ci | utf8mb4 | 255 | | Yes | 1 |
+--------------------------+--------------------+------+------------+-------------+---------+
220 rows in set (0.00 sec)
mysql> SHOW COLLATION WHERE Charset = 'utf8mb4';
+------------------------+---------+------+---------+----------+---------+
| Collation | Charset | Id | Default | Compiled | Sortlen |
+------------------------+---------+------+---------+----------+---------+
| utf8mb4_general_ci | utf8mb4 | 45 | Yes | Yes | 1 |
| utf8mb4_bin | utf8mb4 | 46 | | Yes | 1 |
| utf8mb4_unicode_ci | utf8mb4 | 224 | | Yes | 1 |
| utf8mb4_icelandic_ci | utf8mb4 | 225 | | Yes | 1 |
| utf8mb4_latvian_ci | utf8mb4 | 226 | | Yes | 1 |
| utf8mb4_romanian_ci | utf8mb4 | 227 | | Yes | 1 |
| utf8mb4_slovenian_ci | utf8mb4 | 228 | | Yes | 1 |
| utf8mb4_polish_ci | utf8mb4 | 229 | | Yes | 1 |
| utf8mb4_estonian_ci | utf8mb4 | 230 | | Yes | 1 |
| utf8mb4_spanish_ci | utf8mb4 | 231 | | Yes | 1 |
| utf8mb4_swedish_ci | utf8mb4 | 232 | | Yes | 1 |
| utf8mb4_turkish_ci | utf8mb4 | 233 | | Yes | 1 |
| utf8mb4_czech_ci | utf8mb4 | 234 | | Yes | 1 |
| utf8mb4_danish_ci | utf8mb4 | 235 | | Yes | 1 |
| utf8mb4_lithuanian_ci | utf8mb4 | 236 | | Yes | 1 |
| utf8mb4_slovak_ci | utf8mb4 | 237 | | Yes | 1 |
| utf8mb4_spanish2_ci | utf8mb4 | 238 | | Yes | 1 |
| utf8mb4_roman_ci | utf8mb4 | 239 | | Yes | 1 |
| utf8mb4_persian_ci | utf8mb4 | 240 | | Yes | 1 |
| utf8mb4_esperanto_ci | utf8mb4 | 241 | | Yes | 1 |
| utf8mb4_hungarian_ci | utf8mb4 | 242 | | Yes | 1 |
| utf8mb4_sinhala_ci | utf8mb4 | 243 | | Yes | 1 |
| utf8mb4_german2_ci | utf8mb4 | 244 | | Yes | 1 |
| utf8mb4_croatian_ci | utf8mb4 | 245 | | Yes | 1 |
| utf8mb4_unicode_520_ci | utf8mb4 | 246 | | Yes | 1 |
| utf8mb4_vietnamese_ci | utf8mb4 | 247 | | Yes | 1 |
| utf8mb4_0900_ai_ci | utf8mb4 | 255 | | Yes | 1 |
+------------------------+---------+------+---------+----------+---------+
27 rows in set (0.00 sec)Warning:
TiDB incorrectly treats latin1 as a subset of utf8. This can lead to unexpected behaviors when you store characters that differ between latin1 and utf8 encodings. It is strongly recommended to the utf8mb4 character set. See TiDB #18955 for more details.
Note:
The output of
SHOW COLLATIONandSELECT * FROM information_schema.collationsincludes collations which TiDB does not support. This is fixed in TiDB 3.0, where only supported collations are shown.
For compatibility with MySQL, TiDB will allow other collation names to be used:
mysql> CREATE TABLE t1 (a INT NOT NULL PRIMARY KEY AUTO_INCREMENT, b VARCHAR(10)) COLLATE utf8mb4_unicode_520_ci;
Query OK, 0 rows affected (0.00 sec)
mysql> INSERT INTO t1 VALUES (1, 'a');
Query OK, 1 row affected (0.00 sec)
mysql> SELECT * FROM t1 WHERE b = 'a';
+---+------+
| a | b |
+---+------+
| 1 | a |
+---+------+
1 row in set (0.00 sec)
mysql> SELECT * FROM t1 WHERE b = 'A';
Empty set (0.00 sec)
mysql> SHOW CREATE TABLE t1\G
*************************** 1. row ***************************
Table: t1
Create Table: CREATE TABLE `t1` (
`a` int(11) NOT NULL AUTO_INCREMENT,
`b` varchar(10) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin DEFAULT NULL,
PRIMARY KEY (`a`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_520_ci AUTO_INCREMENT=30002
1 row in set (0.00 sec)Collation naming conventions
The collation names in TiDB follow these conventions:
The prefix of a collation is its corresponding character set, generally followed by one or more suffixes indicating other collation characteristic. For example,
utf8_general_ciandlatin1_swedish_ciare collations for the utf8 and latin1 character sets, respectively. Thebinarycharacter set has a single collation, also namedbinary, with no suffixes.A language-specific collation includes a language name. For example,
utf8_turkish_ciandutf8_hungarian_cisort characters for the utf8 character set using the rules of Turkish and Hungarian, respectively.Collation suffixes indicate whether a collation is case and accent sensitive, or binary. The following table shows the suffixes used to indicate these characteristics.
Suffix Meaning _ai Accent insensitive _as Accent sensitive _ci Case insensitive _cs Case sensitive _bin Binary
Note:
Currently, TiDB only supports some of the collations in the above table.
Database character set and collation
Each database has a character set and a collation. You can use the CREATE DATABASE statement to specify the database character set and collation:
CREATE DATABASE db_name
[[DEFAULT] CHARACTER SET charset_name]
[[DEFAULT] COLLATE collation_name]Where DATABASE can be replaced with SCHEMA.
Different databases can use different character sets and collations. Use the character_set_database and collation_database to see the character set and collation of the current database:
mysql> CREATE SCHEMA test1 CHARACTER SET utf8 COLLATE uft8_general_ci;
Query OK, 0 rows affected (0.09 sec)
mysql> USE test1;
Database changed
mysql> SELECT @@character_set_database, @@collation_database;
+--------------------------|----------------------+
| @@character_set_database | @@collation_database |
+--------------------------|----------------------+
| utf8 | uft8_general_ci |
+--------------------------|----------------------+
1 row in set (0.00 sec)
mysql> CREATE SCHEMA test2 CHARACTER SET latin1 COLLATE latin1_general_ci;
Query OK, 0 rows affected (0.09 sec)
mysql> USE test2;
Database changed
mysql> SELECT @@character_set_database, @@collation_database;
+--------------------------|----------------------+
| @@character_set_database | @@collation_database |
+--------------------------|----------------------+
| latin1 | latin1_general_ci |
+--------------------------|----------------------+
1 row in set (0.00 sec)You can also see the two values in INFORMATION_SCHEMA:
SELECT DEFAULT_CHARACTER_SET_NAME, DEFAULT_COLLATION_NAME
FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME = 'db_name';Table character set and collation
You can use the following statement to specify the character set and collation for tables:
CREATE TABLE tbl_name (column_list)
[[DEFAULT] CHARACTER SET charset_name]
[COLLATE collation_name]]
ALTER TABLE tbl_name
[[DEFAULT] CHARACTER SET charset_name]
[COLLATE collation_name]For example:
mysql> CREATE TABLE t1(a int) CHARACTER SET utf8 COLLATE utf8_general_ci;
Query OK, 0 rows affected (0.08 sec)The table character set and collation are used as the default values for column definitions if the column character set and collation are not specified in individual column definitions.
Column character set and collation
See the following table for the character set and collation syntax for columns:
col_name {CHAR | VARCHAR | TEXT} (col_length)
[CHARACTER SET charset_name]
[COLLATE collation_name]
col_name {ENUM | SET} (val_list)
[CHARACTER SET charset_name]
[COLLATE collation_name]Connection character sets and collations
The server character set and collation are the values of the
character_set_serverandcollation_serversystem variables.The character set and collation of the default database are the values of the
character_set_databaseandcollation_databasesystem variables. You can usecharacter_set_connectionandcollation_connectionto specify the character set and collation for each connection. Thecharacter_set_clientvariable is to set the client character set. Before returning the result, thecharacter_set_resultssystem variable indicates the character set in which the server returns query results to the client, including the metadata of the result.
You can use the following statement to specify a particular collation that is related to the client:
SET NAMES 'charset_name' [COLLATE 'collation_name']SET NAMESindicates what character set the client will use to send SQL statements to the server.SET NAMES utf8indicates that all the requests from the client use utf8, as well as the results from the server.The
SET NAMES 'charset_name'statement is equivalent to the following statement combination:SET character_set_client = charset_name; SET character_set_results = charset_name; SET character_set_connection = charset_name;COLLATEis optional, if absent, the default collation of thecharset_nameis used.SET CHARACTER SET 'charset_name'Similar to
SET NAMES, theSET NAMES 'charset_name'statement is equivalent to the following statement combination:SET character_set_client = charset_name; SET character_set_results = charset_name; SET collation_connection = @@collation_database;
Validity check of characters
For the specified utf8 or utf8mb4 character set, TiDB only supports the valid utf8 character, and reports the incorrect utf8 value error when the character is invalid. This validity check of characters in TiDB is compatible with MySQL 8.0 but incompatible with MySQL 5.7 or earlier versions.
To disable this error reporting, use set @@tidb_skip_utf8_check=1; to skip the character check.
For more information, see Connection Character Sets and Collations in MySQL.
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