Search for a single value in multiple tables

Question

1.50/5 (2 votes)

See more:

I am developing an application in ASP with VB.net.
In this application one user can apply for only one out of four applications. Records of these applications are placed in four tables say t1 , t2, t3, t4.

I want to search if user has already applied for any of the application or not?

All four tables are having different column Names but userID (record) will be same.

Pl help

What I have tried:

Sql = "Select FA.ApplicationID, TFA.ApplicationID, AC.ApplicationID " &
      "FROM (FreshApplications as FA  " &
      "INNER JOIN TempFreshApplications as TFA on U.UPCNo = TFA.UserID) " &
      "INNER JOIN ApplicationsForChange as AC on U.UPCNo = AC.UPCNo" &
      " where U.UPC = '" & Session("LoggedInUPCNo") & "'"

Posted 30-Aug-17 5:04am

mairothia

Updated 30-Aug-17 13:49pm

Add a Solution

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

RossMW · Answer 1 · 2017-08-30T09:52:00

Try using Union All statement

See

https://docs.microsoft.com/en-us/sql/t-sql/language-elements/set-operators-union-transact-sql[^]

So you can do something like

sql = "Select sum(id) as Num from
(
Select count(userid) as id from t1 where userid = " & Session("LoggedInUPCNo") & "
union all
Select count(userid) as id from t2 where userid = " & Session("LoggedInUPCNo") & "
union all
Select count(userid) as id from t3 where userid = " & Session("LoggedInUPCNo") & "
union all
Select count(userid) as id from t4 where userid = " & Session("LoggedInUPCNo") & ") t"

Graeme_Grant · Answer 2 · 2017-08-30T13:49:00

Solution 2

Warning: A good practice is that you should always use parameters and not string concatenation regardless if the query is privately or publicly generated. One day, the query may be made public then it will be open to SQL Injection attacks[^] which will compromise the security of the data.

Posted 30-Aug-17 13:49pm

Graeme_Grant