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DROP INDEX
TiDB 数据库中 DROP INDEX 的使用概况。
/docs-cn/dev/sql-statements/sql-statement-drop-index/
/docs-cn/dev/reference/sql/statements/drop-index/

DROP INDEX

DROP INDEX 语句用于从指定的表中删除索引，并在 TiKV 中将空间标记为释放。

语法图

DropIndexStmt ::=
    "DROP" "INDEX" IfExists Identifier "ON" TableName IndexLockAndAlgorithmOpt

IfExists ::=
    ( 'IF' 'EXISTS' )?

IndexLockAndAlgorithmOpt ::=
    ( LockClause AlgorithmClause? | AlgorithmClause LockClause? )?

示例

{{< copyable "sql" >}}

CREATE TABLE t1 (id INT NOT NULL PRIMARY KEY AUTO_INCREMENT, c1 INT NOT NULL);
Query OK, 0 rows affected (0.10 sec)

{{< copyable "sql" >}}

INSERT INTO t1 (c1) VALUES (1),(2),(3),(4),(5);
Query OK, 5 rows affected (0.02 sec)
Records: 5  Duplicates: 0  Warnings: 0

{{< copyable "sql" >}}

EXPLAIN SELECT * FROM t1 WHERE c1 = 3;
+-------------------------+----------+-----------+---------------+--------------------------------+
| id                      | estRows  | task      | access object | operator info                  |
+-------------------------+----------+-----------+---------------+--------------------------------+
| TableReader_7           | 10.00    | root      |               | data:Selection_6               |
| └─Selection_6           | 10.00    | cop[tikv] |               | eq(test.t1.c1, 3)              |
|   └─TableFullScan_5     | 10000.00 | cop[tikv] | table:t1      | keep order:false, stats:pseudo |
+-------------------------+----------+-----------+---------------+--------------------------------+
3 rows in set (0.00 sec)

{{< copyable "sql" >}}

CREATE INDEX c1 ON t1 (c1);
Query OK, 0 rows affected (0.30 sec)

{{< copyable "sql" >}}

EXPLAIN SELECT * FROM t1 WHERE c1 = 3;
+------------------------+---------+-----------+------------------------+---------------------------------------------+
| id                     | estRows | task      | access object          | operator info                               |
+------------------------+---------+-----------+------------------------+---------------------------------------------+
| IndexReader_6          | 0.01    | root      |                        | index:IndexRangeScan_5                      |
| └─IndexRangeScan_5     | 0.01    | cop[tikv] | table:t1, index:c1(c1) | range:[3,3], keep order:false, stats:pseudo |
+------------------------+---------+-----------+------------------------+---------------------------------------------+
2 rows in set (0.00 sec)

{{< copyable "sql" >}}

DROP INDEX c1 ON t1;
Query OK, 0 rows affected (0.30 sec)

MySQL 兼容性

  • 不支持删除 CLUSTERED 类型的 PRIMARY KEY。要了解关于 CLUSTERED 主键的详细信息，请参考聚簇索引。

另请参阅