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dev/reference/sql: add sql statements (#1425)
* dev/reference/sql: add sql statements * dev/reference/sql: fix aliases in sql statements * Apply suggestions from code review Co-Authored-By: bb7133 <bb7133@gmail.com> * dev/reference/sql: improve wording * Apply suggestions from code review Co-Authored-By: Calvin Weng <wenghao@pingcap.com> * dev/reference/sql: improve wording based on Calvin's suggestions * dev/reference/sql: fix wording * dev/reference/sql: fix alias format * dev/reference/sql: address comments & fix format * dev/reference/sql: add SELECT syntax description * Apply suggestions from code review Co-Authored-By: Lilian Lee <lilin@pingcap.com> * dev/reference/sql: fix links * Update dev/reference/sql/statements/begin.md Co-Authored-By: Lilian Lee <lilin@pingcap.com> * Update dev/reference/sql/statements/kill.md Co-Authored-By: Lilian Lee <lilin@pingcap.com> * Update TOC
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| Original file line number | Diff line number | Diff line change |
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| --- | ||
| title: ADD COLUMN | ||
| summary: TiDB 数据库中 ADD COLUMN 的使用概况。 | ||
| category: reference | ||
| --- | ||
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| # ADD COLUMN | ||
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| `ALTER TABLE.. ADD COLUMN` 语句用于在已有表中添加列。在 TiDB 中，`ADD COLUMN` 为在线操作，不会阻塞表中的数据读写。 | ||
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| ## 语法图 | ||
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| **AlterTableStmt:** | ||
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|  | ||
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| **AlterTableSpec:** | ||
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|  | ||
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| **ColumnKeywordOpt:** | ||
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|  | ||
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| **ColumnDef:** | ||
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|  | ||
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| **ColumnPosition:** | ||
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|  | ||
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| ## 示例 | ||
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| ```sql | ||
| mysql> CREATE TABLE t1 (id INT NOT NULL PRIMARY KEY auto_increment); | ||
| Query OK, 0 rows affected (0.11 sec) | ||
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| mysql> INSERT INTO t1 VALUES (NULL); | ||
| Query OK, 1 row affected (0.02 sec) | ||
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| mysql> SELECT * FROM t1; | ||
| +----+ | ||
| | id | | ||
| +----+ | ||
| | 1 | | ||
| +----+ | ||
| 1 row in set (0.00 sec) | ||
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| mysql> ALTER TABLE t1 ADD COLUMN c1 INT NOT NULL; | ||
| Query OK, 0 rows affected (0.28 sec) | ||
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| mysql> SELECT * FROM t1; | ||
| +----+----+ | ||
| | id | c1 | | ||
| +----+----+ | ||
| | 1 | 0 | | ||
| +----+----+ | ||
| 1 row in set (0.00 sec) | ||
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| mysql> ALTER TABLE t1 ADD c2 INT NOT NULL AFTER c1; | ||
| Query OK, 0 rows affected (0.28 sec) | ||
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| mysql> SELECT * FROM t1; | ||
| +----+----+----+ | ||
| | id | c1 | c2 | | ||
| +----+----+----+ | ||
| | 1 | 0 | 0 | | ||
| +----+----+----+ | ||
| 1 row in set (0.00 sec) | ||
| ``` | ||
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| ## MySQL 兼容性 | ||
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| * 不支持同时添加多列。 | ||
| * 不支持将新添加的列设为 `PRIMARY KEY`。 | ||
| * 不支持将新添加的列设为 `AUTO_INCREMENT`。 | ||
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| ## 另请参阅 | ||
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| * [ADD INDEX](/dev/reference/sql/statements/add-index.md) | ||
| * [CREATE TABLE](/dev/reference/sql/statements/create-table.md) |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,80 @@ | ||
| --- | ||
| title: ADD INDEX | ||
| summary: TiDB 数据库中 ADD INDEX 的使用概况。 | ||
| category: reference | ||
| --- | ||
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| # ADD INDEX | ||
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| `ALTER TABLE.. ADD INDEX` 语句用于在已有表中添加一个索引。在 TiDB 中，`ADD INDEX` 为在线操作，不会阻塞表中的数据读写。 | ||
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| ## 语法图 | ||
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| **AlterTableStmt:** | ||
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|  | ||
|
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| **AlterTableSpec:** | ||
|
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||
|  | ||
|
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| **ColumnKeywordOpt:** | ||
|
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||
|  | ||
|
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| **ColumnDef:** | ||
|
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|  | ||
|
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| **ColumnPosition:** | ||
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|  | ||
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| ## 示例 | ||
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| ```sql | ||
| mysql> CREATE TABLE t1 (id INT NOT NULL PRIMARY KEY auto_increment, c1 INT NOT NULL); | ||
| Query OK, 0 rows affected (0.11 sec) | ||
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| mysql> INSERT INTO t1 (c1) VALUES (1),(2),(3),(4),(5); | ||
| Query OK, 5 rows affected (0.03 sec) | ||
| Records: 5 Duplicates: 0 Warnings: 0 | ||
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| mysql> 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) | ||
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| mysql> ALTER TABLE t1 ADD INDEX (c1); | ||
| Query OK, 0 rows affected (0.30 sec) | ||
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| mysql> 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) | ||
| ``` | ||
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| ## MySQL 兼容性 | ||
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| * 不支持 `FULLTEXT`，`HASH` 和 `SPATIAL` 索引。 | ||
| * 不支持降序索引（类似于 MySQL 5.7）。 | ||
| * 目前尚不支持同时添加多个索引。 | ||
| * 无法向表中添加 `PRIMARY KEY`。 | ||
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| ## 另请参阅 | ||
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| * [CREATE INDEX](/dev/reference/sql/statements/create-index.md) | ||
| * [DROP INDEX](/dev/reference/sql/statements/drop-index.md) | ||
| * [RENAME INDEX](/dev/reference/sql/statements/rename-index.md) | ||
| * [ADD COLUMN](/dev/reference/sql/statements/add-column.md) | ||
| * [CREATE TABLE](/dev/reference/sql/statements/create-table.md) | ||
| * [EXPLAIN](/dev/reference/sql/statements/explain.md) |
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