Question

It’s hard to explain but I have this table, incurredcharges where it has 3 columns (no, patient_no, procedure_no) Ignore the “no” column. The other table that I need is the charges, where the names of the procedures are stored. So I want to output the procedure_no with its corresponding procedure name.

The problem is, “charges” isnt the only table I need. Cause I was so stupid that I separated the procedure names of the ER charge, ultrasound, and the confinement. Therefore producing THREE tables that have the same structures.

    SELECT incurredcharges.procedure_no, incurredcharges.patient_no, charges.procedure
    FROM incurredcharges

    INNER JOIN charges
ON incurredcharges.procedure_no=charges.procedure_no
    WHERE incurredcharges.patient_no=12;

That statement works but it only shows the procedure name FROM the ER charge only. Ultrasound and confinement procedure names will not be shown!

Answer 1

For the immediate need, you can UNION ALL the 3 tables together as a derived table to JOIN against.

SELECT
  `c`.`procedure`, 
  `incurredcharges`.`procedure_no`,
  `incurredcharges`.`patient_no`
FROM
  incurredcharges
  /* UNION ALL the 3 like tables together as a derived table */
  INNER JOIN (
    SELECT `procedure`, `procedure_no` FROM `charges`
    UNION ALL
    SELECT `procedure`, `procedure_no` FROM `confinement`
    UNION ALL
    SELECT `procedure`, `procedure_no` FROM `ultrasound`
  ) c ON `incurredcharges`.`procedure_no` = c.`procedure_no`
WHERE `incurredcharges`.`patient_no` = 12

But for the future:

The correct long-term fix, however, is to use a similar UNION ALL structure as used in the subquery to insert all these records back into a unified table, with a new column that identifies their source.

CREATE TABLE unified_charges AS 
  SELECT `procedure`, `procedure_no`, 'ER' AS `chargetype` FROM `charges`
  UNION ALL
  SELECT `procedure`, `procedure_no`, 'CONFINEMENT' AS `chargetype` FROM `confinement`
  UNION ALL
  SELECT `procedure`, `procedure_no`, 'ULTRASOUND' AS `chargetype` FROM `ultrasound`

Note: procedure is a MySQL reserved keyword that must be quoted with backticks, so I just quoted everything.