mirror of
				https://github.com/MariaDB/server.git
				synced 2025-11-03 14:33:32 +03:00 
			
		
		
		
	- Make the range-et-al optimizer produce E(#table records after table 
                                           condition is applied),
- Make the join optimizer use this value,
- Add "filtered" column to EXPLAIN EXTENDED to show 
  fraction of records left after table condition is applied
- Adjust test results, add comments
mysql-test/r/archive_gis.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/auto_increment.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/bdb_gis.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/bench_count_distinct.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/binlog_stm_blackhole.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/case.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/cast.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/compress.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/ctype_collate.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/ctype_cp1250_ch.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/date_formats.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/distinct.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/fulltext.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_compress.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_crypt.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_default.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_encrypt.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_gconcat.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_group.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_if.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_in.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_like.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_math.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_op.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_regexp.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_set.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_str.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_system.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_test.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_time.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/gis.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/group_by.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/group_min_max.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/having.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/heap.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/heap_hash.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/index_merge.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/index_merge_innodb.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/index_merge_ror.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/innodb_gis.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/insert_update.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/join.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/join_nested.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/key_diff.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/myisam.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/ndb_gis.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/negation_elimination.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/null.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/olap.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/partition_pruning.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/query_cache.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/row.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/rpl_get_lock.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/rpl_master_pos_wait.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/select.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/ssl.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/ssl_compress.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/subselect.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/type_blob.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/union.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/varbinary.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/variables.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/view.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/t/ctype_cp1250_ch.test:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/t/func_like.test:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/t/group_min_max.test:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/t/index_merge_ror.test:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/t/index_merge_ror_cpk.test:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/t/join.test:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/t/partition_pruning.test:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
sql/opt_range.cc:
  BUG#14940: Make range/index_merge/group-min-max optimizer produce TABLE::quick_condition_rows -
    estimate of #records that will match the table condition.
sql/sql_class.cc:
  BUG#14940: Add "filtered" column to output of EXPLAIN EXTENDED
sql/sql_select.cc:
  BUG#14940: 
  - Make the join optimizer to use TABLE::quick_condition_rows=
    = E(#table records after filtering with table condition) 
  - Add "filtered" column to output of EXPLAIN EXTENDED
sql/sql_select.h:
  BUG#14940: Added comments
sql/table.h:
  BUG#14940: Added comments
		
	
		
			
				
	
	
		
			203 lines
		
	
	
		
			8.8 KiB
		
	
	
	
		
			Plaintext
		
	
	
	
	
	
			
		
		
	
	
			203 lines
		
	
	
		
			8.8 KiB
		
	
	
	
		
			Plaintext
		
	
	
	
	
	
drop table if exists t1,t2;
 | 
						|
select CASE "b" when "a" then 1 when "b" then 2 END;
 | 
						|
CASE "b" when "a" then 1 when "b" then 2 END
 | 
						|
2
 | 
						|
select CASE "c" when "a" then 1 when "b" then 2 END;
 | 
						|
CASE "c" when "a" then 1 when "b" then 2 END
 | 
						|
NULL
 | 
						|
select CASE "c" when "a" then 1 when "b" then 2 ELSE 3 END;
 | 
						|
CASE "c" when "a" then 1 when "b" then 2 ELSE 3 END
 | 
						|
3
 | 
						|
select CASE BINARY "b" when "a" then 1 when "B" then 2 WHEN "b" then "ok" END;
 | 
						|
CASE BINARY "b" when "a" then 1 when "B" then 2 WHEN "b" then "ok" END
 | 
						|
ok
 | 
						|
select CASE "b" when "a" then 1 when binary "B" then 2 WHEN "b" then "ok" END;
 | 
						|
CASE "b" when "a" then 1 when binary "B" then 2 WHEN "b" then "ok" END
 | 
						|
ok
 | 
						|
select CASE concat("a","b") when concat("ab","") then "a" when "b" then "b" end;
 | 
						|
CASE concat("a","b") when concat("ab","") then "a" when "b" then "b" end
 | 
						|
a
 | 
						|
select CASE when 1=0 then "true" else "false" END;
 | 
						|
CASE when 1=0 then "true" else "false" END
 | 
						|
false
 | 
						|
select CASE 1 when 1 then "one" WHEN 2 then "two" ELSE "more" END;
 | 
						|
CASE 1 when 1 then "one" WHEN 2 then "two" ELSE "more" END
 | 
						|
one
 | 
						|
explain extended select CASE 1 when 1 then "one" WHEN 2 then "two" ELSE "more" END;
 | 
						|
id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 | 
						|
1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 | 
						|
Warnings:
 | 
						|
Note	1003	select (case 1 when 1 then _latin1'one' when 2 then _latin1'two' else _latin1'more' end) AS `CASE 1 when 1 then "one" WHEN 2 then "two" ELSE "more" END`
 | 
						|
select CASE 2.0 when 1 then "one" WHEN 2.0 then "two" ELSE "more" END;
 | 
						|
CASE 2.0 when 1 then "one" WHEN 2.0 then "two" ELSE "more" END
 | 
						|
two
 | 
						|
select (CASE "two" when "one" then "1" WHEN "two" then "2" END) | 0;
 | 
						|
(CASE "two" when "one" then "1" WHEN "two" then "2" END) | 0
 | 
						|
2
 | 
						|
select (CASE "two" when "one" then 1.00 WHEN "two" then 2.00 END) +0.0;
 | 
						|
(CASE "two" when "one" then 1.00 WHEN "two" then 2.00 END) +0.0
 | 
						|
2.00
 | 
						|
select case 1/0 when "a" then "true" else "false" END;
 | 
						|
case 1/0 when "a" then "true" else "false" END
 | 
						|
false
 | 
						|
select case 1/0 when "a" then "true" END;
 | 
						|
case 1/0 when "a" then "true" END
 | 
						|
NULL
 | 
						|
select (case 1/0 when "a" then "true" END) | 0;
 | 
						|
(case 1/0 when "a" then "true" END) | 0
 | 
						|
NULL
 | 
						|
select (case 1/0 when "a" then "true" END) + 0.0;
 | 
						|
(case 1/0 when "a" then "true" END) + 0.0
 | 
						|
NULL
 | 
						|
select case when 1>0 then "TRUE" else "FALSE" END;
 | 
						|
case when 1>0 then "TRUE" else "FALSE" END
 | 
						|
TRUE
 | 
						|
select case when 1<0 then "TRUE" else "FALSE" END;
 | 
						|
case when 1<0 then "TRUE" else "FALSE" END
 | 
						|
FALSE
 | 
						|
create table t1 (a int);
 | 
						|
insert into t1 values(1),(2),(3),(4);
 | 
						|
select case a when 1 then 2 when 2 then 3 else 0 end as fcase, count(*) from t1 group by fcase;
 | 
						|
fcase	count(*)
 | 
						|
0	2
 | 
						|
2	1
 | 
						|
3	1
 | 
						|
explain extended select case a when 1 then 2 when 2 then 3 else 0 end as fcase, count(*) from t1 group by fcase;
 | 
						|
id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 | 
						|
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	4	100.00	Using temporary; Using filesort
 | 
						|
Warnings:
 | 
						|
Note	1003	select (case `test`.`t1`.`a` when 1 then 2 when 2 then 3 else 0 end) AS `fcase`,count(0) AS `count(*)` from `test`.`t1` group by (case `test`.`t1`.`a` when 1 then 2 when 2 then 3 else 0 end)
 | 
						|
select case a when 1 then "one" when 2 then "two" else "nothing" end as fcase, count(*) from t1 group by fcase;
 | 
						|
fcase	count(*)
 | 
						|
nothing	2
 | 
						|
one	1
 | 
						|
two	1
 | 
						|
drop table t1;
 | 
						|
create table t1 (row int not null, col int not null, val varchar(255) not null);
 | 
						|
insert into t1 values (1,1,'orange'),(1,2,'large'),(2,1,'yellow'),(2,2,'medium'),(3,1,'green'),(3,2,'small');
 | 
						|
select max(case col when 1 then val else null end) as color from t1 group by row;
 | 
						|
color
 | 
						|
orange
 | 
						|
yellow
 | 
						|
green
 | 
						|
drop table t1;
 | 
						|
SET NAMES latin1;
 | 
						|
CREATE TABLE t1 SELECT 
 | 
						|
CASE WHEN 1 THEN _latin1'a' COLLATE latin1_danish_ci ELSE _latin1'a' END AS c1,
 | 
						|
CASE WHEN 1 THEN _latin1'a' ELSE _latin1'a' COLLATE latin1_danish_ci END AS c2,
 | 
						|
CASE WHEN 1 THEN 'a' ELSE  1  END AS c3,
 | 
						|
CASE WHEN 1 THEN  1  ELSE 'a' END AS c4,
 | 
						|
CASE WHEN 1 THEN 'a' ELSE 1.0 END AS c5,
 | 
						|
CASE WHEN 1 THEN 1.0 ELSE 'a' END AS c6,
 | 
						|
CASE WHEN 1 THEN  1  ELSE 1.0 END AS c7,
 | 
						|
CASE WHEN 1 THEN 1.0 ELSE  1  END AS c8,
 | 
						|
CASE WHEN 1 THEN 1.0 END AS c9,
 | 
						|
CASE WHEN 1 THEN 0.1e1 else 0.1 END AS c10,
 | 
						|
CASE WHEN 1 THEN 0.1e1 else 1 END AS c11,
 | 
						|
CASE WHEN 1 THEN 0.1e1 else '1' END AS c12
 | 
						|
;
 | 
						|
SHOW CREATE TABLE t1;
 | 
						|
Table	Create Table
 | 
						|
t1	CREATE TABLE `t1` (
 | 
						|
  `c1` varchar(1) CHARACTER SET latin1 COLLATE latin1_danish_ci NOT NULL DEFAULT '',
 | 
						|
  `c2` varchar(1) CHARACTER SET latin1 COLLATE latin1_danish_ci NOT NULL DEFAULT '',
 | 
						|
  `c3` varbinary(1) NOT NULL DEFAULT '',
 | 
						|
  `c4` varbinary(1) NOT NULL DEFAULT '',
 | 
						|
  `c5` varbinary(4) NOT NULL DEFAULT '',
 | 
						|
  `c6` varbinary(4) NOT NULL DEFAULT '',
 | 
						|
  `c7` decimal(2,1) NOT NULL DEFAULT '0.0',
 | 
						|
  `c8` decimal(2,1) NOT NULL DEFAULT '0.0',
 | 
						|
  `c9` decimal(2,1) DEFAULT NULL,
 | 
						|
  `c10` double NOT NULL DEFAULT '0',
 | 
						|
  `c11` double NOT NULL DEFAULT '0',
 | 
						|
  `c12` varbinary(5) NOT NULL DEFAULT ''
 | 
						|
) ENGINE=MyISAM DEFAULT CHARSET=latin1
 | 
						|
DROP TABLE t1;
 | 
						|
SELECT CASE 
 | 
						|
WHEN 1 
 | 
						|
THEN _latin1'a' COLLATE latin1_danish_ci 
 | 
						|
ELSE _latin1'a' COLLATE latin1_swedish_ci
 | 
						|
END;
 | 
						|
ERROR HY000: Illegal mix of collations (latin1_danish_ci,EXPLICIT) and (latin1_swedish_ci,EXPLICIT) for operation 'case'
 | 
						|
SELECT CASE _latin1'a' COLLATE latin1_general_ci
 | 
						|
WHEN _latin1'a' COLLATE latin1_danish_ci  THEN 1
 | 
						|
WHEN _latin1'a' COLLATE latin1_swedish_ci THEN 2
 | 
						|
END;
 | 
						|
ERROR HY000: Illegal mix of collations (latin1_general_ci,EXPLICIT), (latin1_danish_ci,EXPLICIT), (latin1_swedish_ci,EXPLICIT) for operation 'case'
 | 
						|
SELECT 
 | 
						|
CASE _latin1'a' COLLATE latin1_general_ci  WHEN _latin1'A' THEN '1' ELSE 2 END,
 | 
						|
CASE _latin1'a' COLLATE latin1_bin         WHEN _latin1'A' THEN '1' ELSE 2 END,
 | 
						|
CASE _latin1'a' WHEN _latin1'A' COLLATE latin1_swedish_ci THEN '1' ELSE 2 END,
 | 
						|
CASE _latin1'a' WHEN _latin1'A' COLLATE latin1_bin        THEN '1' ELSE 2 END
 | 
						|
;
 | 
						|
CASE _latin1'a' COLLATE latin1_general_ci  WHEN _latin1'A' THEN '1' ELSE 2 END	CASE _latin1'a' COLLATE latin1_bin         WHEN _latin1'A' THEN '1' ELSE 2 END	CASE _latin1'a' WHEN _latin1'A' COLLATE latin1_swedish_ci THEN '1' ELSE 2 END	CASE _latin1'a' WHEN _latin1'A' COLLATE latin1_bin        THEN '1' ELSE 2 END
 | 
						|
1	2	1	2
 | 
						|
CREATE TABLE t1 SELECT COALESCE(_latin1'a',_latin2'a');
 | 
						|
ERROR HY000: Illegal mix of collations (latin1_swedish_ci,COERCIBLE) and (latin2_general_ci,COERCIBLE) for operation 'coalesce'
 | 
						|
CREATE TABLE t1 SELECT COALESCE('a' COLLATE latin1_swedish_ci,'b' COLLATE latin1_bin);
 | 
						|
ERROR HY000: Illegal mix of collations (latin1_swedish_ci,EXPLICIT) and (latin1_bin,EXPLICIT) for operation 'coalesce'
 | 
						|
CREATE TABLE t1 SELECT 
 | 
						|
COALESCE(1), COALESCE(1.0),COALESCE('a'),
 | 
						|
COALESCE(1,1.0), COALESCE(1,'1'),COALESCE(1.1,'1'),
 | 
						|
COALESCE('a' COLLATE latin1_bin,'b');
 | 
						|
explain extended SELECT 
 | 
						|
COALESCE(1), COALESCE(1.0),COALESCE('a'),
 | 
						|
COALESCE(1,1.0), COALESCE(1,'1'),COALESCE(1.1,'1'),
 | 
						|
COALESCE('a' COLLATE latin1_bin,'b');
 | 
						|
id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 | 
						|
1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 | 
						|
Warnings:
 | 
						|
Note	1003	select coalesce(1) AS `COALESCE(1)`,coalesce(1.0) AS `COALESCE(1.0)`,coalesce(_latin1'a') AS `COALESCE('a')`,coalesce(1,1.0) AS `COALESCE(1,1.0)`,coalesce(1,_latin1'1') AS `COALESCE(1,'1')`,coalesce(1.1,_latin1'1') AS `COALESCE(1.1,'1')`,coalesce((_latin1'a' collate latin1_bin),_latin1'b') AS `COALESCE('a' COLLATE latin1_bin,'b')`
 | 
						|
SHOW CREATE TABLE t1;
 | 
						|
Table	Create Table
 | 
						|
t1	CREATE TABLE `t1` (
 | 
						|
  `COALESCE(1)` int(1) NOT NULL DEFAULT '0',
 | 
						|
  `COALESCE(1.0)` decimal(2,1) NOT NULL DEFAULT '0.0',
 | 
						|
  `COALESCE('a')` varchar(1) NOT NULL DEFAULT '',
 | 
						|
  `COALESCE(1,1.0)` decimal(2,1) NOT NULL DEFAULT '0.0',
 | 
						|
  `COALESCE(1,'1')` varbinary(1) NOT NULL DEFAULT '',
 | 
						|
  `COALESCE(1.1,'1')` varbinary(4) NOT NULL DEFAULT '',
 | 
						|
  `COALESCE('a' COLLATE latin1_bin,'b')` varchar(1) CHARACTER SET latin1 COLLATE latin1_bin NOT NULL DEFAULT ''
 | 
						|
) ENGINE=MyISAM DEFAULT CHARSET=latin1
 | 
						|
DROP TABLE t1;
 | 
						|
SELECT 'case+union+test'
 | 
						|
UNION 
 | 
						|
SELECT CASE LOWER('1') WHEN LOWER('2') THEN 'BUG' ELSE 'nobug' END;
 | 
						|
case+union+test
 | 
						|
case+union+test
 | 
						|
nobug
 | 
						|
SELECT CASE LOWER('1') WHEN LOWER('2') THEN 'BUG' ELSE 'nobug' END;
 | 
						|
CASE LOWER('1') WHEN LOWER('2') THEN 'BUG' ELSE 'nobug' END
 | 
						|
nobug
 | 
						|
SELECT 'case+union+test'
 | 
						|
UNION 
 | 
						|
SELECT CASE '1' WHEN '2' THEN 'BUG' ELSE 'nobug' END;
 | 
						|
case+union+test
 | 
						|
case+union+test
 | 
						|
nobug
 | 
						|
create table t1(a float, b int default 3);
 | 
						|
insert into t1 (a) values (2), (11), (8);
 | 
						|
select min(a), min(case when 1=1 then a else NULL end),
 | 
						|
min(case when 1!=1 then NULL else a end) 
 | 
						|
from t1 where b=3 group by b;
 | 
						|
min(a)	min(case when 1=1 then a else NULL end)	min(case when 1!=1 then NULL else a end)
 | 
						|
2	2	2
 | 
						|
drop table t1;
 | 
						|
CREATE TABLE t1 (EMPNUM INT);
 | 
						|
INSERT INTO t1 VALUES (0), (2);
 | 
						|
CREATE TABLE t2 (EMPNUM DECIMAL (4, 2));
 | 
						|
INSERT INTO t2 VALUES (0.0), (9.0);
 | 
						|
SELECT COALESCE(t2.EMPNUM,t1.EMPNUM) AS CEMPNUM,
 | 
						|
t1.EMPNUM AS EMPMUM1, t2.EMPNUM AS EMPNUM2
 | 
						|
FROM t1 LEFT JOIN t2 ON t1.EMPNUM=t2.EMPNUM;
 | 
						|
CEMPNUM	EMPMUM1	EMPNUM2
 | 
						|
0.00	0	0.00
 | 
						|
2.00	2	NULL
 | 
						|
SELECT IFNULL(t2.EMPNUM,t1.EMPNUM) AS CEMPNUM,
 | 
						|
t1.EMPNUM AS EMPMUM1, t2.EMPNUM AS EMPNUM2
 | 
						|
FROM t1 LEFT JOIN t2 ON t1.EMPNUM=t2.EMPNUM;
 | 
						|
CEMPNUM	EMPMUM1	EMPNUM2
 | 
						|
0.00	0	0.00
 | 
						|
2.00	2	NULL
 | 
						|
DROP TABLE t1,t2;
 |