- Introduction
- Concepts
- Key Features
- Horizontal Scalability
- MySQL Compatible Syntax
- Replicate from and to MySQL
- Distributed Transactions with Strong Consistency
- Cloud Native Architecture
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- Fault Tolerance & Recovery with Raft
- Automatic Rebalancing
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- Fast Import and Restore of Data
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- Reference
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- SQL Statements
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
SET [GLOBAL|SESSION] <variable>
The statement SET [GLOBAL|SESSION] modifies one of TiDB's built in variables, of either SESSION or GLOBAL scope. Note that similar to MySQL, changes to GLOBAL variables will not apply to either existing connections, or the local connection. Only new sessions will reflect the changes to the value.
Synopsis
SetStmt:
Examples
mysql> SHOW GLOBAL VARIABLES LIKE 'sql_mode';
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
| Variable_name | Value |
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
| sql_mode | ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql> SHOW SESSION VARIABLES LIKE 'sql_mode';
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
| Variable_name | Value |
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
| sql_mode | ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql> SET GLOBAL sql_mode = 'STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER';
Query OK, 0 rows affected (0.03 sec)
mysql> SHOW GLOBAL VARIABLES LIKE 'sql_mode';
+---------------+-----------------------------------------+
| Variable_name | Value |
+---------------+-----------------------------------------+
| sql_mode | STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER |
+---------------+-----------------------------------------+
1 row in set (0.00 sec)
mysql> SHOW SESSION VARIABLES LIKE 'sql_mode';
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
| Variable_name | Value |
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
| sql_mode | ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql> SET SESSION sql_mode = 'STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER';
Query OK, 0 rows affected (0.01 sec)
mysql> SHOW SESSION VARIABLES LIKE 'sql_mode';
+---------------+-----------------------------------------+
| Variable_name | Value |
+---------------+-----------------------------------------+
| sql_mode | STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER |
+---------------+-----------------------------------------+
1 row in set (0.00 sec)MySQL compatibility
The following behavior differences apply:
- Changes made with
SET GLOBALwill be propagated to all TiDB instances in the cluster. This differs from MySQL, where changes do not propagate to replicas. - TiDB presents several variables as both readable and settable. This is required for MySQL compatibility, because it is common for both applications and connectors to read MySQL variables. For example: JDBC connectors both read and set query cache settings, despite not relying on the behavior.
- Changes made with
SET GLOBALwill persist through TiDB server restarts. This means thatSET GLOBALin TiDB behaves more similar toSET PERSISTas available in MySQL 8.0 and above.