Can I do a mysql Select, Update and Delete in one query?

Question

Can I say that one of many ways to optimize mysql is to reduce the number of queries?

If that so, can I do this:

- Select \"data\" => $A from tabl         


        

Answer 1

You can't reduce the number of queries - they all do different things - but you could reduce the number of round trips to the database and the number of parses by wrapping it all as a PLSQL function.

However you can't select the data after you've deleted it.....but consider:

CREATE PROCEDURE s_u_d(a)
BEGIN

UPDATE tab_x SET tab_x.avalue=1 WHERE tab_x.another=a;

DELETE FROM tab_y WHERE tab_y.avalue=a;

SELECT * 
FROM tab_x
WHERE tab_x.another=a;

END;

NB - you can also run multiple selects in the same procedure and handle multiple, different shaped result sets, e.g. see this page

Answer 2

Create a stored procedure:

DELIMITER // 

create procedure empproc(in name varchar(255),in fathername varchar(255),in password varchar(255))

begin

        Select * from xemp where uname = name and fname = fathername;

        insert into xemp values(name,fathername,password);

end //
delimiter ;

Java Code.....

import  java.sql.*;

public class StoredProcedure {

    public static void main(String a[])throws Exception {

        Class.forName("com.mysql.jdbc.Driver").newInstance();
        Connection conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/01jim2010","root","");
        CallableStatement calstat=conn.prepareCall("{call empproc(?,?,?)}");
        calstat.setString(1,"Jimit");
        calstat.setString(2,"Temp");
        calstat.setString(3,"Temp");

        ResultSet rs = calstat.executeQuery();
        conn.close();
        calstat.close();

        System.out.println("Your data has been inserted into table.");
      }
}

Answer 3

NO,
only can combine

• DELETE and SELECT
• UPDATE and SELECT

This is not a proper way for mysql optimization simply
because each query come with different query cost.

And in myisam, it involve table level locking for write

Example for UPDATE and SELECT

/* this will update TABLE_A if ID in TABLE_B exist in TABLE_A */
UPDATE TABLE_A, TABLE_B
  SET TABLE_A.SOME_COLUMN=TABLE_B.SOME_COLUMN
WHERE TABLE_A.ID=TABLE_B.ID

/* or */
UPDATE TABLE_A
  SET SOME_COLUMN = (SELECT SOME_COLUMN_B FROM TABLE_B WHERE ... LIMIT 1)

Example for DELETE and SELECT

DELETE FROM TABLE_A WHERE TABLE_A IN(SELECT ID FROM TABLE_B)