DROP TABLE IF EXISTS t1;
show variables like "system_time_zone";
Variable_name	Value
system_time_zone	MET
select @a:=FROM_UNIXTIME(1);
@a:=FROM_UNIXTIME(1)
1970-01-01 01:00:01
Warnings:
Warning	1287	Setting user variables within expressions is deprecated and will be removed in a future release. Consider alternatives: 'SET variable=expression, ...', or 'SELECT expression(s) INTO variables(s)'.
select unix_timestamp(@a);
unix_timestamp(@a)
1
CREATE TABLE t1 (ts int);
INSERT INTO t1 (ts) VALUES (Unix_timestamp('2002-10-27 01:00'));
INSERT INTO t1 (ts) VALUES (Unix_timestamp('2002-10-27 02:00'));
INSERT INTO t1 (ts) VALUES (Unix_timestamp('2002-10-27 03:00'));
INSERT INTO t1 (ts) VALUES (Unix_timestamp('2002-10-27 02:00'));
INSERT INTO t1 (ts) VALUES (Unix_timestamp('2002-10-27 01:00'));
INSERT INTO t1 (ts) VALUES (Unix_timestamp('2002-10-27 02:00'));
INSERT INTO t1 (ts) VALUES (Unix_timestamp('2003-03-30 02:59:59'));
INSERT INTO t1 (ts) VALUES (Unix_timestamp('2003-03-30 03:00:00'));
INSERT INTO t1 (ts) VALUES (Unix_timestamp('2003-03-30 03:59:59'));
INSERT INTO t1 (ts) VALUES (Unix_timestamp('2003-03-30 04:00:01'));
SELECT ts,from_unixtime(ts) FROM t1;
ts	from_unixtime(ts)
1035673200	2002-10-27 01:00:00
1035680400	2002-10-27 02:00:00
1035684000	2002-10-27 03:00:00
1035680400	2002-10-27 02:00:00
1035673200	2002-10-27 01:00:00
1035680400	2002-10-27 02:00:00
1048986000	2003-03-30 03:00:00
1048986000	2003-03-30 03:00:00
1048989599	2003-03-30 03:59:59
1048989601	2003-03-30 04:00:01
DROP TABLE t1;
CREATE TABLE t1 (ts timestamp);
INSERT IGNORE INTO t1 (ts) VALUES ('2003-03-30 01:59:59'),
('2003-03-30 02:59:59'),
('2003-03-30 03:00:00');
Warnings:
Warning	1299	Invalid TIMESTAMP value in column 'ts' at row 2
DROP TABLE t1;
select unix_timestamp('1970-01-01 01:00:00'), 
unix_timestamp('1970-01-01 01:00:01'),
unix_timestamp('2038-01-19 04:14:07'),
unix_timestamp('2038-01-19 04:14:08');
unix_timestamp('1970-01-01 01:00:00')	unix_timestamp('1970-01-01 01:00:01')	unix_timestamp('2038-01-19 04:14:07')	unix_timestamp('2038-01-19 04:14:08')
0	1	2147483647	0
CREATE TABLE t1 (c1 TIMESTAMP);
SET TIME_ZONE = '+00:00';
SET explicit_defaults_for_timestamp=OFF;
Warnings:
Warning	1287	'explicit_defaults_for_timestamp' is deprecated and will be removed in a future release.
INSERT INTO t1 VALUES('2019-10-27 00:47:42'), ('2019-10-27 00:47:42');
INSERT INTO t1 VALUES('2019-10-27 01:47:42'), ('2019-10-27 01:47:42');
SET TIME_ZONE = 'SYSTEM';
SELECT DISTINCT c1 FROM t1;
c1
2019-10-27 02:47:42
SELECT COUNT(*) FROM t1 GROUP BY c1;
ERROR HY000: Grouping on temporal is non-deterministic for timezones having DST. Please consider switching to UTC for this query.
SET sql_mode='';
SELECT COUNT(*) FROM t1 GROUP BY c1;
ERROR HY000: Grouping on temporal is non-deterministic for timezones having DST. Please consider switching to UTC for this query.
SET sql_mode=DEFAULT;
SET explicit_defaults_for_timestamp=ON;
DROP TABLE t1;