SQL get row count from every table tenantwise-CodePudding

I am working on a multitenant application. Most of the tables contain a column tenant_id. I want the number of rows in all tables for a particular tenant_id.

Example, Tables:-

create table Employee(id integer, name varchar(100), tenantid integer);
insert into Employee(id, name, tenantid) values(1, "Stephan", 64);
insert into Employee(id, name, tenantid) values(2, "Alan", 64);
insert into Employee(id, name, tenantid) values(3, "Charles", 46);

create table Student(id integer, name varchar(100), standard integer, tenantid integer);
insert into Student(id, name, standard, tenantid) values(1, "James", 2, 64);
insert into Student(id, name, standard, tenantid) values(2, "Rony", 4, 64);
insert into Student(id, name, standard, tenantid) values(3, "Steve",6, 64);

create table Teacher(id integer, name varchar(100), subject varchar(100), tenantid integer);
insert into Teacher(id, name, subject, tenantid) values(1, "Alvin", "Science", 46);
insert into Teacher(id, name, subject, tenantid) values(2, "Neil", "Geography", 64);
insert into Teacher(id, name, subject, tenantid) values(3, "Amy", "Mathematics", 46);`

Sample result to get number of rows in every table having tenantid = 64

TableName	Count
Employee	2
Student	3
Teacher	1

How do I loop through all the tables and query where tenantid = <tenantid>

CodePudding user response：

Use Dynamic Query. Form the query dynamically for each table and use string_agg() to concatenate it and execute the query using sp_executesql

declare @tables varchar(max),
        @tenantid int,
        @sql nvarchar(max)

select @tables = 'Employee,Student,Teacher',
       @tenantid = 64;

select @sql = string_agg('select [TableName] = '''   value   ''', [Count] = count(*) from '   quotename(value)   ' where tenantid = @tenantid', ' union all'   char(13) )
from   string_split(@tables, ',')

print @sql

exec sp_executesql @sql, N'@tenantid int', @tenantid

db<>fiddle demo

CodePudding user response：

Use UNION ALL:

SELECT 'Employee' AS "TableName", COUNT(*) AS "Count" FROM Employee WHERE tenantid = 64
UNION ALL
SELECT 'Student' AS "TableName", COUNT(*) AS "Count" FROM Student WHERE tenantid = 64
UNION ALL
SELECT 'Teacher' AS "TableName", COUNT(*) AS "Count" FROM Teacher WHERE tenantid = 64

View example (I'm not sure about efficiency):

CREATE VIEW some_counters_view AS
SELECT 'Employee' AS "TableName", tenantid FROM Employee
UNION ALL
SELECT 'Student' AS "TableName", tenantid FROM Student
UNION ALL
SELECT 'Teacher' AS "TableName", tenantid FROM Teacher
;

SELECT "TableName", COUNT(*) AS "Count"
FROM some_counters_view 
WHERE tenantid = 64
GROUP BY "TableName"