MySQL: SELECT from different tables with a common ID

Question

this is my first post after hundreds of times I've visited your site.

Simple question.

I have Two Tables, indipendent, different in all, with only one common column. We call it ID_Client

I don't have to modify these tables but I want to merge them and make on this a Select Query.

Table A

Col_ID    |Col 1    |Col 2    |Col 3    |
----------|---------|---------|---------|
40302025  |50       |  60     |  70     |
40302028  |50       |  60     |  70     |
40302030  |50       |  60     |  70     |
40302055  |50       |  60     |  70     |
40302074  |50       |  60     |  70     |

Table B

Col_ID    |Col X    |Col Y    |Col Z    |
----------|---------|---------|---------|
40302025  |ABC      |  CDE    |  7ASE   |
40302028  |ABC      |  CDE    |  7ASE   |
40302030  |ABC      |  CDE    |  7ASE   |
40302055  |ABC      |  CDE    |  7ASE   |
40302074  |ABC      |  CDE    |  7ASE   |

Table results

Col_ID    |Col X    |Col Y    |Col Z    |Col 1    |Col 2    |Col 3    |
----------|---------|---------|---------|---------|---------|---------|
40302055  |ABC      |  CDE    |  7ASE   |50       |  60     |  70     |
40302074  |ABC      |  CDE    |  7ASE   |50       |  60     |  70     |

I have to query (like "Order", "Limit" and so on) so that the first table is dependent on the second and vice versa.

Example: I want to sort the column 2 of Table A, based on the X column of Table B where ID> 40302030

Example 2: I want to select column 3 of Table A and column B of Table X where ID> 40302030

I do not want the query to solve these examples, but I want to understand what function should I use. I tried UNION, UNION ALL, JOIN but maybe I did not understand the optics of use.

It sounds like "I want to merge two table in one and then I make the query like SELECT, ORDER BY, WHERE etc."

Thanks and sorry for my english

Carlo

Answer 1

You should JOIN the two tables. Something like this:

SELECT
  a.col_ID,
  b.colx,
  b.coly,
  b.colz,
  a.col1,
  a.col2,
  a.col3
FROM tableA AS a
INNER JOIN tableB AS b ON a.col_ID = b.col_ID
WHERE a.col_ID > 40302030;

See it in action here:

• SQL Fiddle Demo

The results:

|   COL_ID | COLX | COLY | COLZ | COL1 | COL2 | COL3 |
------------------------------------------------------
| 40302055 |  ABC |  CDE | 7ASE |   50 |   60 |   70 |
| 40302074 |  ABC |  CDE | 7ASE |   50 |   60 |   70 |

For sorting add an ORDER BY clause.

---

Since the two table relates to each others, then you should JOIN them.

You might need to use UNION if you want to merge the columns of the two tables in to one set of columns, and I think this isn't the case. Since you want to display all the columns from tablea and all the columns from the tableb.