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

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 table X
- Update $A from table Y
- Delete $A from table X
in one query?

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

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)

Answer 3

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.");
}
}