mysql、oracle、postgreSQL等数据库信息，表信息sql

• MYSQL

#获取数据库的所有表名，注释，表类型，行数，创建时间，占用内存及引擎
select TABLE_NAME,TABLE_COMMENT,TABLE_TYPE,TABLE_ROWS,CREATE_TIME,((DATA_LENGTH+INDEX_LENGTH)/1024/1024) as EVERY_MEMORY,ENGINE " +
    "from information_schema.TABLES WHERE TABLE_SCHEMA = 'test';
#获取表的列名，列类型，字段长度
SELECT COLUMN_NAME,DATA_TYPE,COLUMN_COMMENT,CHARACTER_MAXIMUM_LENGTH as DATA_LENGTH FROM information_schema.COLUMNS WHERE TABLE_Name = 'person';

• ORACLE

#获取数据库的所有表名，行数，占用内存
select table_name,num_rows as table_rows,blocks * 8 /1024 from user_tables;
#获取表的列名，列类型，字段长度
select table_name,column_name,data_type,data_length from all_tab_columns where table_name = 'person';

• POSTGRESQL

#获取数据库的所有表名，注释，表类型，行数，创建时间，占用内存
SELECT  table_name,table_type,pg_relation_size('"' || table_schema || '"."' || table_name || '"') as every_memory,obj_description(oid,'pg_class') as table_comment,reltuples as table_rows
FROM information_schema.tables t1,pg_class t2
WHERE table_schema = 'public' AND t1."table_name" = t2."relname";
#获取表的列名，列类型，字段长度
select table_name,column_name,udt_name as data_type,character_maximum_length as data_length from information_schema.columns a where a.table_name= 'person';