Query multiple tables using one join - sql

Question

I need to query multiple tables that contain the column name 'idClient' for a specific condition.
So far I acquire the tables that I need to query using the following query:
SELECT c.name AS 'ColumnName',
t.name AS 'TableName'
FROM sys.columns c (nolock)
JOIN sys.tables t (nolock) ON c.object_id = t.object_id
WHERE c.name LIKE '%idClient%'
ORDER BY TableName,
ColumnName;
This gives me the following result (in reality there are roughly 100 tables returned):
+------------+-----------------+
| ColumnName | TableName |
+------------+-----------------+
| idClient | tbClient |
| idClient | tbClientContact |
| idClient | tbInvoice |
+------------+-----------------+
In order for me to find all client records in each of the tables I am currently running 3 separate queries for each table name. For example:
SELECT * FROM tbClientContact (nolock)
JOIN tbClient (nolock)
ON tbClientContact.idClient = tbClient.idClient
WHERE tbClient.vcSurname = 'Smith'
Instead of running the above query 3 times for each table, is there an easier way to run the same query on all results that are returned as TableName?
GOAL: I have been tasked with - in the example above - removing any client records from a database where the client surname is 'Smith'. I am running the above SELECT query to find whether the idClient of all clients with the surname of 'Smith' will leave orphan records in tables where there is a link of 'idClient'. I am joining tbClient as the column vcSurname does not exist in any other table than tbClient.

Answer 1

You could try
SELECT idClient FROM tbClient WHERE vcSurname = 'Smith'
UNION ALL
SELECT idClient FROM tbClientContact WHERE vcSurname = 'Smith'
UNION ALL
SELECT idClient FROM tbInvoice WHERE vcSurname = 'Smith'
If you need more columns output, all three queries must have the same number of ouput columns and all of the same type
Edit
As others have suggested, it would be helpful to know what you are doing as the method you are attempting is never the best way of doing something. However, the cursor solution below should build a dynamic query to do what you want
DECLARE #table AS NVARCHAR(128)
DECLARE #sql AS NVARCHAR(4000)
DECLARE c CURSOR FOR
-- hey all the tables with the columns LIKE '%idClient%'
SELECT t.name AS 'TableName'
FROM sys.columns c (nolock)
JOIN sys.tables t (nolock) ON c.object_id = t.object_id
WHERE c.name LIKE '%idClient%'
ORDER BY TableName
-- loop through the results of the query line by line
OPEN c
FETCH NEXT FROM c INTO #table
WHILE ##FETCH_STATUS = 0
BEGIN
-- build the query dynamically
SET #sql =CONCAT(#sql,'SELECT idClient FROM ' + #table + ' WHERE vcSurname = ''Smith'' UNION ALL ')
FETCH NEXT FROM c INTO #table
END
-- remove last "UNION ALL" text
SET #sql = STUFF(#sql,LEN(#sql)-9,11,'')
EXEC sp_executesql #stmt = #sql
CLOSE c
DEALLOCATE c
EDIT EDIT
Just seen your edit. Does your table have foreign / primary key pairs, do the foreign keys have ON DELETE CASCADE? If so, it should just be a case of
DELETE from tbClient WHERE vcSurname = 'Smith'

Answer 2

For automated query:
After question Edit:
SELECT 'SELECT '+c.name+' FROM '+t.name+' T WITH(nolock)
JOIN tbClient (NOLOCK)
ON T.idClient = tbClient.idClient
WHERE vcSurname = ''Smith''
UNION ALL
'
FROM sys.columns c (nolock)
JOIN sys.tables t (nolock) ON c.object_id = t.object_id
WHERE c.name LIKE '%idClient%'
PRINT the result in text format (ctrl+T).
Copy the complete result and then remove last UNION ALL

Answer 3

1 Determine involved tables by querying systables (sysforeignkeys or syscolumns if you don't have FKs).
2 Manually write a comprehensive stored proc that is meant to do everything right
create proc dbo.Client_Del
#client_id int
as
begin try
if not exists(select 1 from dbo.Client c where c.id = #client_id)
raiserror("Client %d not found", 16, 1, #client_id)
begin tran
delete ct
from dbo.ClientContacts ct
where ct.client_id = #client_id
delete idt
from dbo.InvoiceDetail idt
inner join dbo.Invoice i
on i.invoice_id = idt.invoice_id
where i.client_id = #client_id
delete i
from dbo.Invoice i
where i.client_id = #client_id
delete c
from dbo.Client c
where c.client_id = #client_id
commit tran
end try
begin catch
if ##trancount > 0
rollback tran
throw
end catch
GO
3 Invoke your stored proc with an argument
declare #id int
set #id = (select c.client_id from dbo.Client c where c.LastName = 'Smith')
exec dbo.Client_Del
#client_id = #id

Answer 4

I am not sure on what is your need. And this post is enhanced code of #Luv. Use of this, you just run it.
declare #select nvarchar(max) = N''
set #select =
N'
declare #sql nvarchar(max) = N''''
SELECT #sql += '' UNION ALL SELECT ''+c.name+'' FROM ''+t.name+'' T WITH(nolock)
JOIN tbClient (NOLOCK)
ON T.idClient = tbClient.idClient
WHERE vcSurname = ''''Smith''''''
FROM sys.columns c (nolock)
JOIN sys.tables t (nolock) ON c.object_id = t.object_id
WHERE c.name LIKE ''%yourColumnName%''
set #sql = STUFF(#sql, 1, 10, '''')
print #sql
exec sp_executesql #sql
'
exec sp_executesql #select