Question

我想输出为从名称为“ T_”的数据库获取所有表。我写了查询，它获取所有表名。但我不希望将查询作为“从数据库联合中的所有表中选择count（*）”

表示我想获得

select count(*) from T1 UNION
select count(*) from T2 UNION
select count(*) from T3 UNION...

，依此类推有1000行，所以我想要一个查询，查询本身将输出count（*）查询。

select 'select count(*) from ' + table_name from INFORMATION_SCHEMA.TABLES where table_type='BASE TABLE' 
and left(table_name,2) = 'T_'
order by TABLE_NAME

此查询给出所有select count(*) table names like T_*

select 'select count(*) from ' + table_name from INFORMATION_SCHEMA.TABLES where table_type='BASE TABLE' 
and left(table_name,2) = 'T_'
order by TABLE_NAME
+'UNION';

获取输出

select count(*) from T_T1
select count(*) from T_T2
select count(*) from T_T3

预期产量

select count(*) from T_T1 UNION
select count(*) from T_T2 UNION
select count(*) from T_T3 UNION

Answer 1

order by TABLE_NAME + ' UNION'表示您想按TABLE_NAME的值排序，并将其与字符串UNION串联在一起（不会改变任何内容）

您需要在您的UNION：UNION ALL中放入SELECT（实际上我在这里建议...table_type='BASE TABLE' + N' UNION ALL '。）

我还建议将table_name更改为QUOTENAME(table_name)。向您提供以下最终查询：

SELECT N'SELECT COUNT(*) FROM' + QUOTENAME(TABLE_NAME) +  NCHAR(13) + NCHAR(10) + N'UNION ALL'
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_TYPE = 'BASE TABLE'
  AND LEFT(TABLE_NAME, 2) = 'T_'
ORDER BY TABLE_NAME;

Answer 2

select 'select count(*) from ' + table_name + ' UNION ' from INFORMATION_SCHEMA ...

字符串+按+字符串选择查询顺序;

2 个答案: