Question

I have two tables table1 = records, table2 = duplicates. Both tables contain a variable number of columns at any given time and they both contain the exact same columns with the exception of table2 having an additional ID column… Both tables contain a column, user_id. The data comes from a CSV import. If the user_id already exists in table1 it is inserted into table2.

With table2 I need to be able to grab all the rows and print them out in a table, no problem. The part I’m having a hard time figuring out… For each column in table2 that gets printed I need to check if the data matches(based on the user_id) the data in table1 and somehow flag it… (maybe a different color background on the table cell)

Example:

table1 contains the row:

user_id | user_name
-------------------
2342342 | some name

and table2:

user_id | user_name
-------------------
2342342 | different name

then the output would be:

-----------------------------------------
|2342342 | *flag* different name *flag* |
-----------------------------------------

Any idea as to how I could make this work? If it helps any, I’m building this app with Codeigniter.

Answer 1

This query will select all the entries from table2, and if the name is different than the name in table1, is_different will be 1, otherwise it’s 0:

SELECT
    table2.user_name,
    IF(table2.user_name != table1.user_name, 1, 0) AS is_different
FROM
    table2
LEFT JOIN
    table1
ON
    table1.user_id = table2.user_id

EDIT

You can do several of those tests in one query, if you need to compare more than one column:

SELECT
    table2.user_name,
    table2.user_email,
    IF(table2.user_name != table1.user_name, 1, 0) AS is_name_different,
    IF(table2.user_email != table1.user_email, 1, 0) AS is_email_different
FROM
    ...