Use SQL to query all database names and table names of mysql, sersql, oracle

MySQL

• 1. Query all databases

show databases;

• 2. Query all table names in the specified database

use 数据库名
show tables；

or

select table_name from information_schema.tables where table_schema='数据库名' and table_type='BASE TABLE';

• 3. Query all field names in the specified table

select column_name from information_schema.columns where table_schema='数据库名' and table_name='表名';

• 4. Query all field names and field types in the specified table

show create table 表名;

or

select column_name,data_type from information_schema.columns where table_schema='数据库名' and table_name='表名';

SQLServer

1. query all databases

select * from sysdatabases;

2. Query all table names in the current database

select * from sysobjects where xtype='U';
xtype='U':表示所有用户表，xtype='S':表示所有系统表。

3. Query all field names in the specified table

select name from syscolumns where id=Object_Id('table_name');

4. Query all field names and field types in the specified table

select sc.name,st.name from syscolumns sc,systypes st where sc.xtype=st.xtype and sc.id in(select id from sysobjects where xtype='U' and name='table_name');

Oracle

1. Query all databases
   Since Oralce has no database name, only table space, so Oracle does not provide database name query support, only provides table space name query.

select * from v$tablespace;--查询表空间(需要一定权限)

2. Query all table names in the current database

select * from user_tables;

3. Query all field names in the specified table

select column_name from user_tab_columns where table_name = 'table_name';--表名要全大写

4. Query all field names and field types in the specified table

select column_name, data_type from user_tab_columns where table_name = 'table_name';--表名要全大写