MySQL - UPDATE query based on SELECT Query

Question

I need to check (from the same table) if there is an association between two events based on date-time.

One set of data will contain the ending date-time of certain

Answer 1

For same table,

UPDATE PHA_BILL_SEGMENT AS PHA,
     (SELECT BILL_ID, COUNT(REGISTRATION_NUMBER) AS REG 
       FROM PHA_BILL_SEGMENT
        GROUP BY REGISTRATION_NUMBER, BILL_DATE, BILL_AMOUNT
        HAVING REG > 1) T
    SET PHA.BILL_DATE = PHA.BILL_DATE + 2
 WHERE PHA.BILL_ID = T.BILL_ID;

Answer 2

If somebody is seeking to update data from one database to another no matter which table they are targeting, there must be some criteria to do it.

This one is better and clean for all levels:

UPDATE dbname1.content targetTable

LEFT JOIN dbname2.someothertable sourceTable ON
    targetTable.compare_field= sourceTable.compare_field
SET
    targetTable.col1  = sourceTable.cola,
    targetTable.col2 = sourceTable.colb, 
    targetTable.col3 = sourceTable.colc, 
    targetTable.col4 = sourceTable.cold 

Traaa! It works great!

With the above understanding, you can modify the set fields and "on" criteria to do your work. You can also perform the checks, then pull the data into the temp table(s) and then run the update using the above syntax replacing your table and column names.

Hope it works, if not let me know. I will write an exact query for you.

Answer 3

You can actually do this one of two ways:

MySQL update join syntax:

UPDATE tableA a
INNER JOIN tableB b ON a.name_a = b.name_b
SET validation_check = if(start_dts > end_dts, 'VALID', '')
-- where clause can go here

ANSI SQL syntax:

UPDATE tableA SET validation_check = 
    (SELECT if(start_DTS > end_DTS, 'VALID', '') AS validation_check
        FROM tableA
        INNER JOIN tableB ON name_A = name_B
        WHERE id_A = tableA.id_A)

Pick whichever one seems most natural to you.

Answer 4

Easy in MySQL:

UPDATE users AS U1, users AS U2 
SET U1.name_one = U2.name_colX
WHERE U2.user_id = U1.user_id

Answer 5

I had an issue with duplicate entries in one table itself. Below is the approaches were working for me. It has also been advocated by @sibaz.

Finally I solved it using the below queries:

1. The select query is saved in a temp table

   IF OBJECT_ID(N'tempdb..#New_format_donor_temp', N'U') IS NOT NULL
       DROP TABLE #New_format_donor_temp;
   
   select *
   into #New_format_donor_temp
   from DONOR_EMPLOYMENTS
   where DONOR_ID IN (
     1, 2
   )
   
   -- Test New_format_donor_temp
   -- SELECT *
   -- FROM #New_format_donor_temp;
   

2. The temp table is joined in the update query.

   UPDATE de
   SET STATUS_CD=de_new.STATUS_CD, STATUS_REASON_CD=de_new.STATUS_REASON_CD, TYPE_CD=de_new.TYPE_CD
   FROM DONOR_EMPLOYMENTS AS de
     INNER JOIN #New_format_donor_temp AS de_new ON de_new.EMP_NO = de.EMP_NO
   WHERE
     de.DONOR_ID IN (
       3, 4
   )
   

I not very experienced with SQL please advise any better approach you know.

Above queries are for MySql server.

Answer 6

UPDATE
    `table1` AS `dest`,
    (
        SELECT
            *
        FROM
            `table2`
        WHERE
            `id` = x
    ) AS `src`
SET
    `dest`.`col1` = `src`.`col1`
WHERE
    `dest`.`id` = x
;

Hope this works for you.