check if sql column exists after select query

Question

I have this simple query:

  var select = "select * from mainTable where username = '" + username + "'"

where I am then checking this:

 for (var i = 0; i < rows.length; i++) {
           if (rows[i]["CHILDTABLEID"] != undefined) {
              //here I need to check if childtable2id has been created within that table yet
   }
  }

I need to check if childtable2id has been created within that table yet. How is this possible. I was hoping it wouldn't require a modification to my query, and I could just do something along the lines of:

if (rows[I]["CHILDTABLE2ID"]) //check if its been created????

if you get where im trying to go with this.

thanks for the help

Can you provide more detail as to what you're trying to achieve? Also, are you trying to see if the table _has a specific column defined in the schema_ or _has a value set in that column_? — Anthony Forloney, May 31 '21 at 19:25
I am basically querying my table, and then wanting to check if a column has been created yet. If the column does not exist in the table, then right now it will just present an error, but I want to be able to add the column if it doesn't exist. Not sure if that helps — Gianluca, May 31 '21 at 19:26
You might be interested in, https://stackoverflow.com/questions/133031/how-to-check-if-a-column-exists-in-a-sql-server-table to query against the schema for a particular column rather than getting all columns from a `SELECT` — Anthony Forloney, May 31 '21 at 19:29

score 0 · Answer 1 · answered May 31 '21 at 19:40

If your front end knows it wants CHILDTABLE2ID then it should select it:

SELECT CHILDTABLE2ID, ... FROM mainTable WHERE ...

One of two things* happens:

it works
it errors because the column doesn't exist

Your front end will be able to be coded so it can tell the difference

*well, of course it could error for other reasons.. but the front end will still be able to be programmed to tell the difference

check if sql column exists after select query

1 Answers1