How to pass table name as parameter in select statement in SQL Sever - sql

Question

Table:
Col
------
Table1
table2
table3
Query:
select count(*)
from #tablename
I wanted to pass table1, table2, table3 as parameters for #tablename in the select query and get the count for each table
Desired output:
2 (table 1 count) 3 (table 2 count) 4 (table 3 count)

Answer 1

you can use dynamic sql and a cursor to run through them:
Create temp table for testing:
DECLARE #tablenametable TABLE(tablename VARCHAR(100));
INSERT INTO #tablenametable
VALUES('table1'), ('table2'), ('table3');
Use a cursor to run through all tablenames in the table
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;
Give the following results:
select count(*) from table1
select count(*) from table2
select count(*) from table3
Just change PRINT(#SQL) to EXEC(#SQL) when your happy with it

Answer 2

You can use dynamic sql query.
Query
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);
Find a demo here

Answer 3

As mentioned here, you have to use dynamic SQL.
First approach is where you specify table name yourself:
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)
Second approach lets you use table with names of tables:
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)
The result of it will be:
TableName Count
Table1 3
Table2 6
Table3 4

Answer 4

You can use sys.dm_db_partition_stats like this [1]:
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
One line output version will be:
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('');
output:
2 (Table1 count) 3 (table2 count) 4 (table3 count)