如何在SQL Sever的select语句中将表名作为参数传递

Question

表：

Col 
------
Table1 
table2 
table3

查询：

select count(*) 
from @tablename

我想将table1，table2，table3作为@tablename的参数传递给select查询并获取每个表的计数

期望的输出：

 2 (table 1 count)  3 (table 2 count)  4 (table 3 count)

Answer 1

您可以使用动态sql和游标来运行它们：

创建用于测试的临时表：

DECLARE @tablenametable TABLE(tablename VARCHAR(100));
INSERT INTO @tablenametable
VALUES('table1'), ('table2'), ('table3');

使用游标运行表

中的所有表名

DECLARE @tablename VARCHAR(100);
DECLARE dbcursor CURSOR
FOR
    SELECT tablename
    FROM @tablenametable;
OPEN dbcursor;
FETCH NEXT FROM dbcursor INTO @tablename;
WHILE @@FETCH_STATUS = 0
    BEGIN
        DECLARE @sql VARCHAR(MAX);
        SET @sql = 'select count(*) from '+@tablename;
        PRINT(@sql);
        FETCH NEXT FROM dbcursor INTO @tablename;
    END;
CLOSE dbcursor;
DEALLOCATE dbcursor;

给出以下结果：

select count(*) from table1
select count(*) from table2
select count(*) from table3

当您对此感到满意时，只需将PRINT(@SQL)更改为EXEC(@SQL)

Answer 2

您可以使用动态SQL查询。

<强>查询

declare @sql as varchar(max);

select @sql = stuff((
    select ' union all '
    + 'select cast(count(*) as varchar(100)) 
    + ' + char(39) + '(' + [Col] +' Count)' + char(39) 
    + ' as [table_counts] '
    + ' from ' + [col]
    from [your_table_name]
    for xml path('')
  )
  , 1, 11, ''
);

exec(@sql);

的 Find a demo here

Answer 3

如前所述，您必须使用动态SQL。

第一种方法是自己指定表名：

declare @tablename varchar(30), @SQL varchar(30)
set @tablename = 'Table1' --here you specify the name
set @SQL = concat('SELECT COUNT(*) FROM ', @tablename) --here you build the query

EXEC(@SQL)

第二种方法允许您使用具有表名称的表：

declare @SQL varchar(8000)
set @SQL = ''
declare @TableNames table(name varchar(30))
insert into @TableNames values ('Table1'), ('Table2'), ('Table3')
--here you build the query
select @SQL = @SQL + ' SELECT ''' + name + ''' AS [TableName], COUNT(*) AS [Count] FROM ' + name + ' UNION ALL' from @TableNames
-- get rid of last "UNION ALL"
set @SQL = LEFT(@SQL, LEN(@SQL) - 10)
--execute the query
EXEC(@SQL)

结果将是：

TableName    Count
Table1       3
Table2       6
Table3       4

Answer 4

您可以像{sup> [1] 一样使用sys.dm_db_partition_stats：

select
    t.col tableName, sum(s.row_count) tableCount
from 
    yourTable t
join
    sys.dm_db_partition_stats s
  on
    (object_name(s.object_id) = t.col )
 and 
    (s.index_id < 2)
group by 
    t.col;

[1]. Related answer

一行输出版本为：

select
    sum(s.row_count), ' ('+t.col +' count) '
from 
    yourTable t
join
    sys.dm_db_partition_stats s
  on
    (object_name(s.object_id) = t.col )
 and 
    (s.index_id < 2)
group by 
    t.col
for xml path('');

输出：

2 (Table1 count) 3 (table2 count) 4 (table3 count)