Comparison of a YEAR column to DECIMAL and DOUBLE literal works differently in different function and operators:

DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (a YEAR);

INSERT INTO t1 VALUES (2000);

SELECT a=2000.1 AS c1, CASE a WHEN 2000.1 THEN TRUE ELSE FALSE END AS c2, NULLIF(a,2000.1) AS c3, GREATEST(a,2000.1) AS c4 FROM t1;

returns:

+------+------+------+--------+

| c1   | c2   | c3   | c4     |

+------+------+------+--------+

|    1 |    0 | NULL | 2000.1 |

+------+------+------+--------+

That means:

• for c1 it compared as YEAR
• for c2 it compared as DECIMAL
• for c3 it compared as YEAR
• for c4 it compared as DECIMAL

It should work the same way in all functions. Perhaps it should always compare as follows:

• YEAR vs DECIMAL as DECIMAL
• YEAR vs DOUBLE as DOUBLE

Another option would be to compare:

• YEAR vs DECIMAL as YEAR
• YEAR vs DOUBLE as YEAR