ALTER TABLE
ALTER TABLE
ALTER TABLE 语句用于对已有表进行修改，以符合新表结构。ALTER TABLE 语句可用于：
语法图
AlterTableStmt:
TableName:
AlterTableSpec:
示例
{{< copyable "sql" >}}
CREATE TABLE t1 (id INT NOT NULL PRIMARY KEY auto_increment, c1 INT NOT NULL);Query OK, 0 rows affected (0.11 sec){{< copyable "sql" >}}
INSERT INTO t1 (c1) VALUES (1),(2),(3),(4),(5);Query OK, 5 rows affected (0.03 sec)
Records: 5 Duplicates: 0 Warnings: 0{{< copyable "sql" >}}
EXPLAIN SELECT * FROM t1 WHERE c1 = 3;+---------------------+----------+------+-------------------------------------------------------------+
| id | count | task | operator info |
+---------------------+----------+------+-------------------------------------------------------------+
| TableReader_7 | 10.00 | root | data:Selection_6 |
| └─Selection_6 | 10.00 | cop | eq(test.t1.c1, 3) |
| └─TableScan_5 | 10000.00 | cop | table:t1, range:[-inf,+inf], keep order:false, stats:pseudo |
+---------------------+----------+------+-------------------------------------------------------------+
3 rows in set (0.00 sec){{< copyable "sql" >}}
ALTER TABLE t1 ADD INDEX (c1);Query OK, 0 rows affected (0.30 sec){{< copyable "sql" >}}
EXPLAIN SELECT * FROM t1 WHERE c1 = 3;+-------------------+-------+------+-----------------------------------------------------------------+
| id | count | task | operator info |
+-------------------+-------+------+-----------------------------------------------------------------+
| IndexReader_6 | 10.00 | root | index:IndexScan_5 |
| └─IndexScan_5 | 10.00 | cop | table:t1, index:c1, range:[3,3], keep order:false, stats:pseudo |
+-------------------+-------+------+-----------------------------------------------------------------+
2 rows in set (0.00 sec)MySQL 兼容性
- 支持除空间类型外的所有数据类型。
- 不支持
FULLTEXT，HASH和SPATIAL索引。