- 文档中心
- 关于 TiDB
- 快速上手
- 部署标准集群
- 数据迁移
- 运维操作
- 监控与告警
- 故障诊断
- 性能调优
- 系统调优
- 软件调优
- SQL 性能调优
- SQL 性能调优概览
- 理解 TiDB 执行计划
- SQL 优化流程
- 控制执行计划
- 教程
- TiDB 工具
- 功能概览
- 适用场景
- 工具下载
- TiUP
- TiDB Operator
- Dumpling
- TiDB Lightning
- TiDB Data Migration
- Backup & Restore (BR)
- TiDB Binlog
- TiCDC
- TiUniManager
- sync-diff-inspector
- TiSpark
- 参考指南
- 架构
- 监控指标
- 安全加固
- 权限
- SQL
- SQL 语言结构和语法
- SQL 语句
ADD COLUMN
ADD INDEX
ADMIN
ADMIN CANCEL DDL
ADMIN CHECKSUM TABLE
ADMIN CHECK [TABLE|INDEX]
ADMIN SHOW DDL [JOBS|QUERIES]
ALTER DATABASE
ALTER INDEX
ALTER INSTANCE
ALTER TABLE
ALTER USER
ANALYZE TABLE
BACKUP
BEGIN
CHANGE COLUMN
CHANGE DRAINER
CHANGE PUMP
COMMIT
CREATE [GLOBAL|SESSION] BINDING
CREATE DATABASE
CREATE INDEX
CREATE ROLE
CREATE SEQUENCE
CREATE TABLE LIKE
CREATE TABLE
CREATE USER
CREATE VIEW
DEALLOCATE
DELETE
DESC
DESCRIBE
DO
DROP [GLOBAL|SESSION] BINDING
DROP COLUMN
DROP DATABASE
DROP INDEX
DROP ROLE
DROP SEQUENCE
DROP STATS
DROP TABLE
DROP USER
DROP VIEW
EXECUTE
EXPLAIN ANALYZE
EXPLAIN
FLASHBACK TABLE
FLUSH PRIVILEGES
FLUSH STATUS
FLUSH TABLES
GRANT <privileges>
GRANT <role>
INSERT
KILL [TIDB]
LOAD DATA
LOAD STATS
MODIFY COLUMN
PREPARE
RECOVER TABLE
RENAME INDEX
RENAME TABLE
RENAME USER
REPLACE
RESTORE
REVOKE <privileges>
REVOKE <role>
ROLLBACK
SELECT
SET DEFAULT ROLE
SET [NAMES|CHARACTER SET]
SET PASSWORD
SET ROLE
SET TRANSACTION
SET [GLOBAL|SESSION] <variable>
SHOW [BACKUPS|RESTORES]
SHOW ANALYZE STATUS
SHOW [GLOBAL|SESSION] BINDINGS
SHOW BUILTINS
SHOW CHARACTER SET
SHOW COLLATION
SHOW [FULL] COLUMNS FROM
SHOW CONFIG
SHOW CREATE SEQUENCE
SHOW CREATE TABLE
SHOW CREATE USER
SHOW DATABASES
SHOW DRAINER STATUS
SHOW ENGINES
SHOW ERRORS
SHOW [FULL] FIELDS FROM
SHOW GRANTS
SHOW INDEX [FROM|IN]
SHOW INDEXES [FROM|IN]
SHOW KEYS [FROM|IN]
SHOW MASTER STATUS
SHOW PLUGINS
SHOW PRIVILEGES
SHOW [FULL] PROCESSSLIST
SHOW PROFILES
SHOW PUMP STATUS
SHOW SCHEMAS
SHOW STATS_HEALTHY
SHOW STATS_HISTOGRAMS
SHOW STATS_META
SHOW STATUS
SHOW TABLE NEXT_ROW_ID
SHOW TABLE REGIONS
SHOW TABLE STATUS
SHOW [FULL] TABLES
SHOW [GLOBAL|SESSION] VARIABLES
SHOW WARNINGS
SHUTDOWN
SPLIT REGION
START TRANSACTION
TABLE
TRACE
TRUNCATE
UPDATE
USE
WITH
- 数据类型
- 函数与操作符
- 聚簇索引
- 约束
- 生成列
- SQL 模式
- 事务
- 垃圾回收 (GC)
- 视图
- 分区表
- 字符集和排序规则
- 系统表
mysql
- INFORMATION_SCHEMA
- Overview
ANALYZE_STATUS
CLIENT_ERRORS_SUMMARY_BY_HOST
CLIENT_ERRORS_SUMMARY_BY_USER
CLIENT_ERRORS_SUMMARY_GLOBAL
CHARACTER_SETS
CLUSTER_CONFIG
CLUSTER_HARDWARE
CLUSTER_INFO
CLUSTER_LOAD
CLUSTER_LOG
CLUSTER_SYSTEMINFO
COLLATIONS
COLLATION_CHARACTER_SET_APPLICABILITY
COLUMNS
DATA_LOCK_WAITS
DDL_JOBS
DEADLOCKS
ENGINES
INSPECTION_RESULT
INSPECTION_RULES
INSPECTION_SUMMARY
KEY_COLUMN_USAGE
METRICS_SUMMARY
METRICS_TABLES
PARTITIONS
PROCESSLIST
SCHEMATA
SEQUENCES
SESSION_VARIABLES
SLOW_QUERY
STATISTICS
TABLES
TABLE_CONSTRAINTS
TABLE_STORAGE_STATS
TIDB_HOT_REGIONS
TIDB_INDEXES
TIDB_SERVERS_INFO
TIDB_TRX
TIFLASH_REPLICA
TIKV_REGION_PEERS
TIKV_REGION_STATUS
TIKV_STORE_STATUS
USER_PRIVILEGES
VIEWS
METRICS_SCHEMA
- UI
- CLI
- 命令行参数
- 配置文件参数
- 系统变量
- 存储引擎
- 遥测
- 错误码
- 通过拓扑 label 进行副本调度
- 常见问题解答 (FAQ)
- 版本发布历史
- 发布版本汇总
- v5.1
- v5.0
- v4.0
- v3.1
- v3.0
- v2.1
- v2.0
- v1.0
- 术语表
重要
你正在查看 TiDB 数据库的较旧版本 (TiDB v5.1) 的文档。
如无特殊需求,建议使用 TiDB 数据库的最新 LTS 版本。
KEY_COLUMN_USAGE
KEY_COLUMN_USAGE
表描述了列的键约束,比如主键约束。
USE information_schema;
DESC key_column_usage;
+-------------------------------+--------------+------+------+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------------------------+--------------+------+------+---------+-------+
| CONSTRAINT_CATALOG | varchar(512) | NO | | NULL | |
| CONSTRAINT_SCHEMA | varchar(64) | NO | | NULL | |
| CONSTRAINT_NAME | varchar(64) | NO | | NULL | |
| TABLE_CATALOG | varchar(512) | NO | | NULL | |
| TABLE_SCHEMA | varchar(64) | NO | | NULL | |
| TABLE_NAME | varchar(64) | NO | | NULL | |
| COLUMN_NAME | varchar(64) | NO | | NULL | |
| ORDINAL_POSITION | bigint(10) | NO | | NULL | |
| POSITION_IN_UNIQUE_CONSTRAINT | bigint(10) | YES | | NULL | |
| REFERENCED_TABLE_SCHEMA | varchar(64) | YES | | NULL | |
| REFERENCED_TABLE_NAME | varchar(64) | YES | | NULL | |
| REFERENCED_COLUMN_NAME | varchar(64) | YES | | NULL | |
+-------------------------------+--------------+------+------+---------+-------+
12 rows in set (0.00 sec)
SELECT * FROM key_column_usage WHERE table_schema='mysql' and table_name='user';
*************************** 1. row ***************************
CONSTRAINT_CATALOG: def
CONSTRAINT_SCHEMA: mysql
CONSTRAINT_NAME: PRIMARY
TABLE_CATALOG: def
TABLE_SCHEMA: mysql
TABLE_NAME: user
COLUMN_NAME: Host
ORDINAL_POSITION: 1
POSITION_IN_UNIQUE_CONSTRAINT: NULL
REFERENCED_TABLE_SCHEMA: NULL
REFERENCED_TABLE_NAME: NULL
REFERENCED_COLUMN_NAME: NULL
*************************** 2. row ***************************
CONSTRAINT_CATALOG: def
CONSTRAINT_SCHEMA: mysql
CONSTRAINT_NAME: PRIMARY
TABLE_CATALOG: def
TABLE_SCHEMA: mysql
TABLE_NAME: user
COLUMN_NAME: User
ORDINAL_POSITION: 2
POSITION_IN_UNIQUE_CONSTRAINT: NULL
REFERENCED_TABLE_SCHEMA: NULL
REFERENCED_TABLE_NAME: NULL
REFERENCED_COLUMN_NAME: NULL
2 rows in set (0.00 sec)
KEY_COLUMN_USAGE
表中列的含义如下:
CONSTRAINT_CATALOG
:约束所属的目录的名称。该值始终为def
。CONSTRAINT_SCHEMA
:约束所属的数据库的名称。CONSTRAINT_NAME
:约束名称。TABLE_CATALOG
:表所属目录的名称。该值始终为def
。TABLE_SCHEMA
:表所属的架构数据库的名称。TABLE_NAME
:具有约束的表的名称。COLUMN_NAME
:具有约束的列的名称。ORDINAL_POSITION
:列在约束中的位置,而不是列在表中的位置。列位置从 1 开始编号。POSITION_IN_UNIQUE_CONSTRAINT
:唯一约束和主键约束为空。对于外键约束,此列是被引用的表的键的序号位置。REFERENCED_TABLE_SCHEMA
:约束引用的数据库的名称。目前在 TiDB 中,除了外键约束,其它约束此列的值都为nil
。REFERENCED_TABLE_NAME
:约束引用的表的名称。目前在 TiDB 中,除了外键约束,其它约束此列的值都为nil
。REFERENCED_COLUMN_NAME
:约束引用的列的名称。目前在 TiDB 中,除了外键约束,其它约束此列的值都为nil
。
文档内容是否有帮助?