MySQL: select a row if that row is equal for every user

MySQL

In my database I have 5 fix users, lets say user1, …, user5.

Furthermore I have a table

month(name, finished, month, year)

where name is VARCHAR (the name of one of the five users) and the others are INTEGER. In row finished, 0 means not finished and 1 means finished (Note that finished does not mean 'the month is over' in this context). Every user has an entry for each month.
I'm struggling to find a query which returns me the months where every user has the entry finished = 1.

SELECT month FROM month

obviously returns months, where other users can have finished=0

SELECT month FROM month WHERE finished=1

returns the finished months (multiple times), while other users can have finished=0 in this same month and I would have to check in the code if there are months appearing five times (which would mean that month is finished by all users).

Now, without creating triggers or similiar constructs, is there a way to check the desired requirement directly in the SQL-query?

Addendum: I know that a table monthAll(month, year, finishedAll) would be a solution, but setting it to finishedAll=1 if all five users have finished a certain month would equally require additional code in my JavaScript due to the fact how the whole program is constructed.

Best Answer

If there are 5 rows per month (1 for every user), this will do:

SELECT m.year, m.month 
FROM month AS m
GROUP BY m.year, m.month
HAVING SUM(finished) = 5 ;

Related Solutions

Mysql – How to select using the same fields from an undetermined number of tables using MySQL

You can have the information_schema build the entire query for you and execute it as Dynamic SQL (Prepared Statements as @a1ex07 first mentioned):

SELECT CONCAT('SELECT * FROM (SELECT bar_id,bar_weight FROM ',
GROUP_CONCAT(tb SEPARATOR
' WHERE foo_id=1 UNION SELECT bar_id,bar_weight FROM '),
' WHERE foo_id=1) as res order by res.bar_weight desc limit 0, 5')
INTO @foo_query FROM
(
    select CONCAT(table_schema,'.',table_name) tb
    from information_schema.tables
    where table_name like 'foo_reference%'
) A;
SELECT @foo_query\G
PREPARE stmt FROM @foo_query;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

First, let's make some sample tables with sample data:

DROP DATABASE IF EXISTS timpost1;
DROP DATABASE IF EXISTS timpost2;
CREATE DATABASE timpost1;
CREATE DATABASE timpost2;
use timpost1
CREATE TABLE cookie_cutter
(
    foo_id int,
    bar_id int,
    bar_weight int,
    primary key (foo_id)
) ENGINE=MyISAM;
CREATE TABLE timpost1.foo_reference1 LIKE timpost1.cookie_cutter;
CREATE TABLE timpost1.foo_reference2 LIKE timpost1.cookie_cutter;
CREATE TABLE timpost1.foo_reference3 LIKE timpost1.cookie_cutter;
CREATE TABLE timpost2.foo_reference1 LIKE timpost1.cookie_cutter;
CREATE TABLE timpost2.foo_reference2 LIKE timpost1.cookie_cutter;
CREATE TABLE timpost2.foo_reference3 LIKE timpost1.cookie_cutter;
INSERT INTO timpost1.foo_reference1 VALUES (1,17,10),(2,3,20);
INSERT INTO timpost1.foo_reference2 VALUES (1,27,90),(2,3,20);
INSERT INTO timpost1.foo_reference3 VALUES (1,37,40),(2,3,20);
INSERT INTO timpost2.foo_reference1 VALUES (1,47,70),(2,3,20);
INSERT INTO timpost2.foo_reference2 VALUES (1,57,20),(2,3,20);
INSERT INTO timpost2.foo_reference3 VALUES (1,67,50),(2,3,20);

Here are the sample tables being made and loaded:

mysql> DROP DATABASE IF EXISTS timpost1;
Query OK, 4 rows affected (0.03 sec)

mysql> DROP DATABASE IF EXISTS timpost2;
Query OK, 3 rows affected (0.02 sec)

mysql> CREATE DATABASE timpost1;
Query OK, 1 row affected (0.00 sec)

mysql> CREATE DATABASE timpost2;
Query OK, 1 row affected (0.00 sec)

mysql> use timpost1
Database changed
mysql> CREATE TABLE cookie_cutter
    -> (
    ->     foo_id int,
    ->     bar_id int,
    ->     bar_weight int,
    ->     primary key (foo_id)
    -> ) ENGINE=MyISAM;
Query OK, 0 rows affected (0.03 sec)

mysql> CREATE TABLE timpost1.foo_reference1 LIKE timpost1.cookie_cutter;
Query OK, 0 rows affected (0.05 sec)

mysql> CREATE TABLE timpost1.foo_reference2 LIKE timpost1.cookie_cutter;
Query OK, 0 rows affected (0.05 sec)

mysql> CREATE TABLE timpost1.foo_reference3 LIKE timpost1.cookie_cutter;
Query OK, 0 rows affected (0.05 sec)

mysql> CREATE TABLE timpost2.foo_reference1 LIKE timpost1.cookie_cutter;
Query OK, 0 rows affected (0.06 sec)

mysql> CREATE TABLE timpost2.foo_reference2 LIKE timpost1.cookie_cutter;
Query OK, 0 rows affected (0.05 sec)

mysql> CREATE TABLE timpost2.foo_reference3 LIKE timpost1.cookie_cutter;
Query OK, 0 rows affected (0.05 sec)

mysql> INSERT INTO timpost1.foo_reference1 VALUES (1,17,10),(2,3,20);
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> INSERT INTO timpost1.foo_reference2 VALUES (1,27,90),(2,3,20);
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> INSERT INTO timpost1.foo_reference3 VALUES (1,37,40),(2,3,20);
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> INSERT INTO timpost2.foo_reference1 VALUES (1,47,70),(2,3,20);
Query OK, 2 rows affected (0.02 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> INSERT INTO timpost2.foo_reference2 VALUES (1,57,20),(2,3,20);
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> INSERT INTO timpost2.foo_reference3 VALUES (1,67,50),(2,3,20);
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql>

Now let's build the query and execute it:

mysql> SELECT CONCAT('SELECT * FROM (SELECT bar_id,bar_weight FROM ',
    -> GROUP_CONCAT(tb SEPARATOR
    -> ' WHERE foo_id=1 UNION SELECT bar_id,bar_weight FROM '),
    -> ' WHERE foo_id=1) as res order by res.bar_weight desc limit 0, 5')
    -> INTO @foo_query FROM
    -> (
    ->     select CONCAT(table_schema,'.',table_name) tb
    ->     from information_schema.tables
    ->     where table_name like 'foo_reference%'
    -> ) A;
Query OK, 1 row affected (0.02 sec)

mysql> SELECT @foo_query\G
*************************** 1. row ***************************
@foo_query: SELECT * FROM (SELECT bar_id,bar_weight FROM timpost1.foo_reference1 WHERE foo_id=1 UNION SELECT bar_id,bar_weight FROM timpost1.foo_reference2 WHERE foo_id=1 UNION SELECT bar_id,bar_weight FROM timpost1.foo_reference3 WHERE foo_id=1 UNION SELECT bar_id,bar_weight FROM timpost2.foo_reference1 WHERE foo_id=1 UNION SELECT bar_id,bar_weight FROM timpost2.foo_reference2 WHERE foo_id=1 UNION SELECT bar_id,bar_weight FROM timpost2.foo_reference3 WHERE foo_id=1) as res order by res.bar_weight desc limit 0, 5
1 row in set (0.01 sec)

mysql> PREPARE stmt FROM @foo_query;
Query OK, 0 rows affected (0.01 sec)
Statement prepared

mysql> EXECUTE stmt;
+--------+------------+
| bar_id | bar_weight |
+--------+------------+
|     27 |         90 |
|     47 |         70 |
|     67 |         50 |
|     37 |         40 |
|     57 |         20 |
+--------+------------+
5 rows in set (0.00 sec)

mysql> DEALLOCATE PREPARE stmt;
Query OK, 0 rows affected (0.00 sec)

mysql>

CAVEAT

Notice that the query will cross check all databases in the mysql instance that starts with foo_reference. In the above example, both timpost1 and timpost2 were checked.

Also, notice that the subquery will get 6 rows, and the limit 0,5 properly displays the first 5 rows of the subquery.

Give it a Try !!!

MySQL table design of logging tables

Your new design will make it easier to query across all of the tables without the need to know which tables to union when you write a query.

I'm not sure if you need to worry about the partitioning aspect. It sounds OK, but I've never worked with something like this on this scale (not in MySQL).

If you are worried about the partitioning, you could stay with your current solution, but instead of a new table for every year+month, have 12 tables, one for each month, for all years. At least your unions would be constant.

Best Answer

Related Solutions

Mysql – How to select using the same fields from an undetermined number of tables using MySQL

CAVEAT

MySQL table design of logging tables

Related Question