比较表字段值以在数据库中插入新值

Question

I inherited a website with an existing database structure. I have one table (TABLE1) that has something like the following structure:

POSITION_1_TAGS_PERMITTED  | POSITION_2_TAGS_PERMITTED | POSITION_3_TAGS_PERMITTED
----------------------------------------------------------------------------------
CD                         | EN,CS                     | TECH,CS

TABLE1 has this structure up to 20 columns.

I then have another table (TABLE2) that stores the selected value (also has 20 columns):

POS1_SEL_SYMBOL | POS2_SEL_SYMBOL | POS3_SEL_SYMBOL | POS4_SEL_SYMBOL
---------------------------------------------------------------------
A               | AAPL            |                 | AA

I have the tags for the selected variable in this case the tag for my variable is CS. I'd like to find the position in TABLE1 that has the allowed tags and then look in TABLE2 to see if that position already has an entry in it. In this case it would identify position 3 as the column to add my entry to and then I would write a new update statement to add that entry to the database. Is there an easy way to do this with the column format of my database?

EDIT: If there are multiple tags for the variable I'd like it to search the permitted tags column for any value in it. I tried to update my SQL statement to be something like the following:

SELECT eventid, 
CASE 
WHEN (FIND_IN_SET("S&P", POSITION_1_TAGS_PERMITTED) OR FIND_IN_SET("CS", POSITION_1_TAGS_PERMITTED)) AND POS1_SEL_SYMBOL = ""
THEN 1 
END AS found_col 
FROM TABLE1 
JOIN TABLE2 
USING (eventid) 
WHERE EVENTID='159'

This query doesn't give me the same results as just searching for CS did.

Answer 1

SELECT eventid, 
    CASE
        WHEN FIND_IN_SET('CS', POSITION_1_TAGS_PERMITTED) AND POS1_SEL_SYMBOL = ''
        THEN 1
        WHEN FIND_IN_SET('CS', POSITION_2_TAGS_PERMITTED) AND POS2_SEL_SYMBOL = ''
        THEN 2
        WHEN FIND_IN_SET('CS', POSITION_3_TAGS_PERMITTED) AND POS3_SEL_SYMBOL = ''
        THEN 3
        ...
        WHEN FIND_IN_SET('CS', POSITION_20_TAGS_PERMITTED) AND POS20_SEL_SYMBOL = ''
        THEN 20
    END AS found_col
FROM TABLE1
JOIN TABLE2 USING (eventid)

See SQL Insert in first empty column in a row MySQL error for an UPDATE query that you could adapt using the above structure so that you update the field that's found rather than just returning the column number. But with 20 columns, that query will get really long.