需求场景：
现要查询某个库下50个表每个表的表名和对应的数据量，通过pLsql工具运行sql语句，可以以表格的形式展示(表明在左，对应的数据在右)，也方便导入excel。
百度经验（注.表名必须用单引号，不可使用双引号）：
select 'Customers' as tablename, count(*) as row_count from Customers union all select 'Orders' as tablename, count(*) as row_count from Orders union all ……
我的两个表名：BANK_ACC, BANK_CONTRAL
组织查50个表的sql语句：
select 'BANK_ACC' as tablename, count(*) as row_count from BANK_ACC union all select 'BANK_CONTRAL' as tablename, count(*) as row_count from BANK_CONTRAL union all ...
结果展示(这种结果方便导入excel)：
