MySQL 常用脚本之查看数据库、表结构、约束、索引等信息
2020-06-12 04:13
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文章目录
大家好!我是只谈技术不剪发的 Tony 老师。今天带来的分享是如何查看 MySQL 数据库模式以及数据表的结构,包括字段定义、主键、外键、唯一等约束和索引信息,如何查看表和索引占用的磁盘空间等。
数据库和模式
列出数据库/模式
在 MySQL 中,数据库(database)和模式(schema)是相同的概念,可以使用以下查询列出当前实例中包含的数据库/模式:
-- 方法一 select schema_name as database_name from information_schema.schemata order by schema_name; -- 方法二 show databases; -- 方法三 show schemas;
查询结果中的 information_schema、mysql、performance_schema 以及 sys 属于系统数据库/模式。
列出用户创建的数据库/模式
将系统数据库/模式排除之外就是用户创建的数据库/模式:
select schema_name as database_name from information_schema.schemata where schema_name not in ('information_schema','mysql','performance_schema','sys') order by schema_name;
查看数据库的创建语句
使用 SHOW 命令查看数据库的创建语句:
show create database database_name; show create schema database_name;
数据表
列出某个数据库中的表
查看当前数据库中的表:
-- 方法一 select table_schema as database_name, table_name from information_schema.tables where table_type = 'BASE TABLE' and table_schema = database() order by database_name, table_name; -- 方法二 show tables [LIKE 'pattern' | WHERE expr]; -- 方法三 show table status [LIKE 'pattern' | WHERE expr];
其中,database() 函数返回当前数据库的名称。
查看指定数据库中的表,将查询条件中的 database_name 替换成需要查询的数据库名:
-- 方法一 select table_schema as database_name, table_name from information_schema.tables where table_type = 'BASE TABLE' and table_schema = 'database_name' order by database_name, table_name; -- 方法二 show tables {in | from} database_name [LIKE 'pattern' | WHERE expr]; show tables status {in | from} database_name [LIKE 'pattern' | WHERE expr];
列出所有数据库中的表
select table_schema as database_name, table_name from information_schema.tables where table_type = 'BASE TABLE' order by database_name, table_name;
列出缺少主键的表
select tab.table_schema as database_name, tab.table_name from information_schema.tables tab left join information_schema.table_constraints tco on tab.table_schema = tco.table_schema and tab.table_name = tco.table_name and tco.constraint_type = 'PRIMARY KEY' where tco.constraint_type is null and tab.table_schema not in('mysql', 'information_schema', 'performance_schema', 'sys') and tab.table_type = 'BASE TABLE' -- and tab.table_schema = 'sakila' order by tab.table_schema, tab.table_name;
列出数据库中的 InnoDB 表
select table_schema as database_name, table_name from information_schema.tables where engine = 'InnoDB' and table_type = 'BASE TABLE' -- and schema_name not in ('information_schema','mysql','performance_schema','sys') -- and table_schema = 'database_name' order by table_schema, table_name;
列出数据库中的 MyISAM 表
select table_schema as database_name, table_name from information_schema.tables where engine = 'MyISAM' and table_type = 'BASE TABLE' -- and schema_name not in ('information_schema','mysql','performance_schema','sys') -- and table_schema = 'database_name' order by table_schema, table_name;
查看数据表的存储引擎
select table_schema as database_name, table_name, engine from information_schema.tables where table_type = 'BASE TABLE' -- and schema_name not in ('information_schema','mysql','performance_schema','sys') -- and table_schema = 'database_name' order by table_schema, table_name;
查找最近创建的表
使用以下脚本查找最近 30 天之内创建的表:
select table_schema as database_name, table_name, create_time from information_schema.tables where table_type = 'BASE TABLE' and create_time > adddate(current_date, interval - 30 day) -- and schema_name not in ('information_schema','mysql','performance_schema','sys') -- and table_schema = 'database_name' order by create_time desc, table_name;
查找最近修改的表
使用以下脚本查找最近 30 天之内被修改过的表:
select table_schema as database_name, table_name, update_time from information_schema.tables where table_type = 'BASE TABLE' and update_time > (current_timestamp() - interval 30 day) -- and schema_name not in ('information_schema','mysql','performance_schema','sys') -- and table_schema = 'database_name' order by update_time desc, table_name;
以上查询返回的结果可能不准确,因为update_time 取决于存储引擎,具体可以参考官方文档。
查看表的创建语句
show create table table_name;
字段
列出数据库中所有表的字段
select tab.table_schema as database_schema, tab.table_name as table_name, col.ordinal_position as column_id, col.column_name as column_name, col.data_type as data_type, case when col.numeric_precision is not null then col.numeric_precision else col.character_maximum_length end as max_length, case when col.datetime_precision is not null then col.datetime_precision when col.numeric_scale is not null then col.numeric_scale else 0 end as 'precision' from information_schema.tables as tab join information_schema.columns as col on col.table_schema = tab.table_schema and col.table_name = tab.table_name where tab.table_type = 'BASE TABLE' and tab.table_schema not in ('information_schema','mysql','performance_schema','sys') -- 查看当前数据库中的表 -- and tab.table_schema = database() -- 查看指定数据库中的表 -- and tab.table_schema = 'database_name' order by tab.table_name, col.ordinal_position;
列出数据库中指定表的字段
-- 方法一 desc table_name; -- 方法二 SHOW [EXTENDED] [FULL] {COLUMNS | FIELDS} {FROM | IN} table_name [{FROM | IN} database_name] [LIKE 'pattern' | WHERE expr]; -- 方法二 select ordinal_position as column_id, column_name as column_name, data_type as data_type, case when numeric_precision is not null then numeric_precision else character_maximum_length end as max_length, case when datetime_precision is not null then datetime_precision when numeric_scale is not null then numeric_scale else 0 end as data_precision, is_nullable, column_default from information_schema.columns where table_name = 'tablename' and table_schema = 'schema_name' order by ordinal_position;
列出所有数字类型的字段
select col.table_schema as database_name, col.table_name, col.ordinal_position as col_id, col.column_name, col.data_type, col.numeric_precision, col.numeric_scale from information_schema.columns col join information_schema.tables tab on tab.table_schema = col.table_schema and tab.table_name = col.table_name and tab.table_type = 'BASE TABLE' where col.data_type in ('tinyint', 'smallint', 'mediumint', 'int', 'bigint', 'decimal', 'bit', 'float', 'double') and col.table_schema not in ('information_schema', 'sys', 'performance_schema', 'mysql') -- and col.table_schema = 'database_name' -- and col.table_name = 'table_name' order by col.table_schema, col.table_name, col.ordinal_position;
列出所有字符类型的字段
select col.table_schema as database_name, col.table_name, col.ordinal_position as col_id, col.column_name, col.data_type, col.numeric_precision, col.numeric_scale from information_schema.columns col join information_schema.tables tab on tab.table_schema = col.table_schema and tab.table_name = col.table_name and tab.table_type = 'BASE TABLE' where col.data_type in ('char', 'varchar', 'binary', 'varbinary', 'blob', 'tinyblob', 'mediumblob', 'longblob', 'text', 'tinytext', 'mediumtext', 'longtext' 'enum', 'set') and col.table_schema not in ('information_schema', 'sys', 'performance_schema', 'mysql') -- and col.table_schema = 'database_name' -- and col.table_name = 'table_name' order by col.table_schema, col.table_name, col.ordinal_position;
列出所有日期时间类型的字段
select col.table_schema as database_name, col.table_name, col.ordinal_position as col_id, col.column_name, col.data_type, col.numeric_precision, col.numeric_scale from information_schema.columns col join information_schema.tables tab on tab.table_schema = col.table_schema and tab.table_name = col.table_name and tab.table_type = 'BASE TABLE' where col.data_type in ('date', 'time', 'datetime', 'year', 'timestamp') and col.table_schema not in ('information_schema', 'sys', 'performance_schema', 'mysql') -- and col.table_schema = 'database_name' -- and col.table_name = 'table_name' order by col.table_schema, col.table_name, col.ordinal_position;
列出字段的详细信息
以下查询用于列出字段的详细信息,包括是否主键、外键、唯一、默认值、是否可空以及计算列的表达式等:
select col.table_schema as database_name, col.table_name, col.column_name, col.data_type, case when col.data_type in ('datetime', 'timestamp', 'time') then col.datetime_precision else col.numeric_precision end as 'precision', col.numeric_scale, col.character_maximum_length as char_length, col.column_default, col.generation_expression, case when (group_concat(constraint_type separator ', ')) like '%PRIMARY KEY%' then 'YES' else 'NO' end as PK, case when (group_concat(constraint_type separator ', ')) like '%UNIQUE%' then 'YES' else 'NO' end as UQ, case when (group_concat(constraint_type separator ', ')) like '%FOREIGN KEY%' then 'YES' else 'NO' end as FK, col.is_nullable from information_schema.columns col join information_schema.tables tab on col.table_schema = tab.table_schema and col.table_name = tab.table_name and tab.table_type = 'BASE TABLE' left join information_schema.key_column_usage kcu on col.table_schema = kcu.table_schema and col.table_name = kcu.table_name and col.column_name = kcu.column_name left join information_schema.table_constraints tco on kcu.constraint_schema = tco.constraint_schema and kcu.constraint_name = tco.constraint_name and kcu.table_name = tco.table_name where tab.table_schema not in ('information_schema','mysql','performance_schema','sys') -- 查看当前数据库中的表 -- and tab.table_schema = database() -- 查看指定数据库中的表 -- and tab.table_schema = 'database_name' group by 1,2,3,4,5,6,7,8,9,13 order by col.table_schema, col.table_name, col.column_name;
列出计算列及其表达式
select table_schema as database_name, table_name, column_name, data_type, generation_expression from information_schema.columns where length(generation_expression) > 0 and table_schema not in ('information_schema','mysql','performance_schema','sys') -- 查看当前数据库中的表 -- and table_schema = database() -- 查看指定数据库中的表 -- and table_schema = 'database_name' -- 查看指定表 -- and table_name = 'tablename' order by table_schema, table_name, column_name;
主键、外键、唯一等约束
列出指定数据库中的主键约束
select tab.table_schema as database_schema, sta.index_name as pk_name, sta.seq_in_index as column_id, sta.column_name, tab.table_name from information_schema.tables as tab join information_schema.statistics as sta on sta.table_schema = tab.table_schema and sta.table_name = tab.table_name and sta.index_name = 'primary' where tab.table_schema = 'database_name' and tab.table_type = 'BASE TABLE' order by tab.table_name, column_id;
列出指定数据库中的外键约束
select concat(col.table_schema, '.', col.table_name) as 'foreign_table', col.column_name as column_name, '->' as rel, concat(kcu.referenced_table_schema, '.', kcu.referenced_table_name) as primary_table, kcu.referenced_column_name as pk_column_name, kcu.constraint_name as fk_constraint_name from information_schema.columns col join information_schema.tables tab on col.table_schema = tab.table_schema and col.table_name = tab.table_name left join information_schema.key_column_usage kcu on col.table_schema = kcu.table_schema and col.table_name = kcu.table_name and col.column_name = kcu.column_name where col.table_schema not in('information_schema','sys', 'mysql', 'performance_schema') and tab.table_type = 'BASE TABLE' and kcu.referenced_table_schema is not null and tab.table_schema = 'hrdb' order by col.table_schema, col.table_name, col.ordinal_position;
列出指定数据库中的唯一约束
select stat.table_schema as database_name, stat.table_name, stat.index_name, group_concat(stat.column_name order by stat.seq_in_index separator ', ') as columns, tco.constraint_type from information_schema.statistics stat join information_schema.table_constraints tco on stat.table_schema = tco.table_schema and stat.table_name = tco.table_name and stat.index_name = tco.constraint_name where stat.non_unique = 0 and stat.table_schema not in ('information_schema', 'sys', 'performance_schema', 'mysql') and stat.table_schema = 'database_name' group by stat.table_schema, stat.table_name, stat.index_name, tco.constraint_type order by stat.table_schema, stat.table_name;
列出指定数据库中的字段默认值
select table_schema as database_name, table_name, column_name, column_default from information_schema.columns where column_default is not null and table_schema not in ('information_schema', 'sys', 'performance_schema','mysql') and table_schema = 'database_name' order by table_schema, table_name, ordinal_position;
索引
列出指定数据库中的索引
select table_schema as database_name, table_name, index_name, group_concat(column_name order by seq_in_index) as columns, index_type, case non_unique when 1 then 'Not Unique' else 'Unique' end as is_unique from information_schema.statistics where table_schema not in ('information_schema', 'mysql', 'performance_schema', 'sys') and table_schema = 'database_name' group by table_schema, table_name, index_name, index_type, non_unique order by table_schema, table_name;
列出指定表中的索引
-- 方法一 SHOW [EXTENDED] {INDEX | INDEXES | KEYS} {FROM | IN} table_name [{FROM | IN} database_name] [WHERE expr]; -- 方法二 select table_schema as database_name, table_name, index_name, group_concat(column_name order by seq_in_index) as columns, index_type, case non_unique when 1 then 'Not Unique' else 'Unique' end as is_unique from information_schema.statistics where table_schema not in ('information_schema', 'mysql', 'performance_schema', 'sys') and table_schema = 'database_name' and table_name = 'table_name' group by table_schema, table_name, index_name, index_type, non_unique order by table_schema, table_name;
数据行及大小
查询表中的行数
对于不同的存储引擎使用不同的查询方法:
-- MyISAM 存储引擎表 select table_schema, table_name, table_rows from information_schema.tables where table_type = 'BASE TABLE' and engine = 'MyISAM' and table_schema not in ('information_schema', 'mysql', 'performance_schema', 'sys') -- and table_schema = 'database_name' -- and table_name = 'table_name' order by table_schema, table_name; -- InnoDB 存储引擎表 select count(*) from table_name;
查看表分配和使用的空间
select table_schema as database_name, table_name, round(sum((data_length + index_length)) / power(1024, 2), 2) as used_mb, round(sum((data_length + index_length + data_free)) /power(1024, 2), 2) as allocated_mb, round(sum(data_free) /power(1024, 2), 2) as free_mb from information_schema.tables where table_type = 'BASE TABLE' and table_schema not in ('information_schema', 'mysql', 'performance_schema', 'sys') -- and table_schema = 'database_name' -- and table_name = 'table_name' group by table_schema, table_name order by used_mb desc;
查看表中数据和索引的使用空间
select table_schema as database_name, table_name, engine, round(1.0*data_length/1024/1024, 2) as data_size_mb, round(index_length/1024/1024, 2) as index_size_mb, round((data_length + index_length)/1024/1024, 2) as total_size_mb from information_schema.tables where table_type = 'BASE TABLE' and table_schema not in ('information_schema', 'mysql', 'performance_schema', 'sys') -- and table_schema = 'database_name' -- and table_name = 'table_name' order by t 1c0bc otal_size_mb desc;
对于 InnoDB 表,data_length 字段表示聚集索引的大小(包含了所有的数据)。InnoDB 表的 index_length 和 data_length 返回的是近似值。
查看 InnoDB 辅助索引占用的空间
select database_name, table_name, index_name, (1.0*stat_value*@@innodb_page_size/1024/1024) as index_size_mb from mysql.innodb_index_stats where stat_name = 'size' and index_name not in ('PRIMARY', 'GEN_CLUST_INDEX') -- and database_name = 'database_name' -- and table_name = 'table_name' order by index_size_mb desc;
查看 LOB 大对象占用的空间
select tab.table_schema as database_name, tab.table_name, round(sum(data_length + index_length) / power(1024, 2), 2) as used_mb, round(sum(data_length + index_length + data_free) / power(1024, 2), 2) as allocated_mb from information_schema.tables as tab join information_schema.columns as col on col.table_schema = tab.table_schema and col.table_name = tab.table_name where tab.table_type = 'BASE TABLE' and tab.table_schema not in ('information_schema', 'mysql', 'performance_schema', 'sys') and col.data_type in ('blob', 'mediumblob', 'longblob', 'text', 'mediumtext', 'longtext') -- and tab.table_schema = 'database_name' -- and tab.table_name = 'table_name' group by 1,2 order by 2;
数据库比较
比较两个数据库中的表和字段信息
以下查询比较两个数据库中的所有表,返回任意数据库中越少的字段:
set @database_1 = 'database_name_1'; -- provide first database name here set @database_2 = 'database_name_2'; -- provide second database name here select * from ( select COALESCE(c1.table_name, c2.table_name) as table_name, COALESCE(c1.column_name, c2.column_name) as table_column, c1.column_name as database1, c2.column_name as database2 from (select table_name, column_name from information_schema.columns c where c.table_schema = @database_1) c1 right join (select table_name, column_name from information_schema.columns c where c.table_schema = @database_2) c2 on c1.table_name = c2.table_name and c1.column_name = c2.column_name union select COALESCE(c1.table_name, c2.table_name) as table_name, COALESCE(c1.column_name, c2.column_name) as table_column, c1.column_name as schema1, c2.column_name as schema2 from (select table_name, column_name from information_schema.columns c where c.table_schema = @database_1) c1 left join (select table_name, column_name from information_schema.columns c where c.table_schema = @database_2) c2 on c1.table_name = c2.table_name and c1.column_name = c2.column_name ) tmp where database1 is null or database2 is null order by table_name, table_column; set @database_1 = null; set @database_2 = null;
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