Trying to get my delete statement to work - sql

Question

I want to remove rows from a table, based on a column from another table as such:
Table1: Table2:
value value, i
If table2.i is less than 1, delete corresponding row from table1 (but keep it in table2).
The problem is that value isn't unique, so if I have this for exampe:
Table1 table2
+-------+ +-----------+
| value | | value | i |
+-------+ +-----------+
| 5 | | 5 | 0 |
| 3 | | 5 | 3 |
+-------+ | 3 | 0 |
| 3 | 0 |
+-----------+
Value 3 should be deleted from table1 (since all occurrences in table2 has i<1) but value 5 should stay(because of i=3 row in table2)
My code so far (doesn't work):
DELETE FROM Table1, Table2
WHERE (SELECT MIN(Table2.i) FROM Table1, Table2
WHERE Table1.value = Table2.value) < 1;
Problem is: since my subquery returns min for ALL rows, everything gets deleted.
And I can't use "group by" in my subquery because then my comparison isn't allowed.

Answer 1

Try this one:
DELETE FROM Table1
WHERE NOT EXISTS(SELECT 1
FROM Table2
WHERE Table2.i > 0
AND Table2.value = Table1.value)

Answer 2

I dont know why you are using min, instead u should use max:
try this
DELETE FROM Table1
WHERE Table1.value1 = Table2.value1
and (SELECT MAX(Table2.i) FROM Table2
WHERE Table1.value1 = Table2.value1) < 1;

Answer 3

Ok, I'd start by writing a query that selects the rows you want to delete,
SELECT
*
FROM
Table1
EXCEPT
(
SELECT
t1.value
FROM
Table1 t1
JOIN
Table2 t2
ON t2.value = t1.value
WHERE
t2.i > 0
);
See Fiddle
Then change the SELECT to a DELETE
DELETE Table1
FROM
Table1 t1
WHERE
t1.value NOT IN
(
SELECT
t1.value
FROM
Table1 t1
JOIN
Table2 t2
ON t2.value = t1.value
WHERE
t2.i > 0
);
See Fiddle

Answer 4

How about:
delete from table1 where value in
(select value from table2 group by value having max(i) < 1)
Grouping table 2 by value and using having to detect where the maximum is less than 1 allows you to select the correct values for deletion from table 1.
having is basically a where clause which comes into play after aggregation so can be used with max and so on.
Here's a script to show it in action:
DROP TABLE TABLE1;
DROP TABLE TABLE2;
CREATE TABLE TABLE1 (VALUE INTEGER);
CREATE TABLE TABLE2 (VALUE INTEGER, I INTEGER);
INSERT INTO TABLE1 VALUES (5);
INSERT INTO TABLE1 VALUES (3);
INSERT INTO TABLE2 VALUES (5, 0);
INSERT INTO TABLE2 VALUES (5, 3);
INSERT INTO TABLE2 VALUES (3, 0);
INSERT INTO TABLE2 VALUES (3, 0);
SELECT * FROM TABLE1;
SELECT * FROM TABLE2;
DELETE FROM TABLE1 WHERE VALUE IN
(SELECT VALUE FROM TABLE2 GROUP BY VALUE HAVING MAX(I) = 0);
SELECT * FROM TABLE1;
SELECT * FROM TABLE2;
The output of this script is shown below. First, the setting up of all the tables:
DROP TABLE TABLE1; DROP TABLE TABLE2;
TABLE1 DROPPED
TABLE2 DROPPED
CREATE TABLE TABLE1 (VALUE INTEGER);
TABLE1 CREATED
CREATE TABLE TABLE2 (VALUE INTEGER, I INTEGER);
TABLE2 CREATED
INSERT INTO TABLE1 VALUES ((5), (3));
INSERTED 2 ROWS
INSERT INTO TABLE2 VALUES ((5, 0), (5, 3), (3,0), 3, 0));
INSERTED 4 ROWS
And display them to ensure they're as expected:
SELECT * FROM TABLE1; SELECT * FROM TABLE2;
VALUE
-----
5
3
VALUE I
----- -
5 0
5 3
3 0
3 0
Then run the command to get rid of the relevant rows:
DELETE FROM TABLE1 WHERE VALUE IN
(SELECT VALUE FROM TABLE2 GROUP BY VALUE HAVING MAX(I) = 0);
DELETED 1 ROW
And you can see that the 3` row has disappeared from table 1 as desired:
SELECT * FROM TABLE1; SELECT * FROM TABLE2;
VALUE
-----
5
VALUE I
----- -
5 0
5 3
3 0
3 0