Bug #119140 DISTINCT works inconsistently in normal SELECT and prepared statement for 0 and -0

• Submitted: 13 Oct 8:01
• Reporter: chi zhang
• Status: Open
• Category: MySQL Server
• Severity: S1 (Critical)
• Version: 9.4.0
• OS: Any
• CPU Architecture: Any

[13 Oct 8:01] chi zhang

Description:
Hi,

In the following test case, there are two equivalent queries, one is a normal SELECT, and the other is a prepared statement. But they have different results.

```
CREATE TABLE t2(c0 DOUBLE) ;
INSERT INTO t2(c0) VALUES(0), ("-0.0");
SELECT DISTINCT IF((NULL) NOT IN (t2.c0), "1", NULL) AS ref0, t2.c0 AS ref1 FROM t2;
-- NULL    0

SET @a = NULL;
SET @b = NULL;
PREPARE prepare_query FROM 'SELECT DISTINCT IF((?) NOT IN (t2.c0), "1", ?) AS ref0, t2.c0 AS ref1  FROM t2';
EXECUTE prepare_query USING @a,@b;
-- NULL    0
-- NULL    -0
```

How to repeat:
```
CREATE TABLE t2(c0 DOUBLE) ;
INSERT INTO t2(c0) VALUES(0), ("-0.0");
SELECT DISTINCT IF((NULL) NOT IN (t2.c0), "1", NULL) AS ref0, t2.c0 AS ref1 FROM t2;
-- NULL    0

SET @a = NULL;
SET @b = NULL;
PREPARE prepare_query FROM 'SELECT DISTINCT IF((?) NOT IN (t2.c0), "1", ?) AS ref0, t2.c0 AS ref1  FROM t2';
EXECUTE prepare_query USING @a,@b;
-- NULL    0
-- NULL    -0
```