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drop table if exists t1,t2;
create table t1 (
c_id int(11) not null default '0',
org_id int(11) default null,
unique key contacts$c_id (c_id),
key contacts$org_id (org_id)
) engine=innodb;
insert into t1 values
(2,null),(120,null),(141,null),(218,7), (128,1),
(151,2),(234,2),(236,2),(243,2),(255,2),(259,2),(232,3),(235,3),(238,3),
(246,3),(253,3),(269,3),(285,3),(291,3),(293,3),(131,4),(230,4),(231,4);
create table t2 (
slai_id int(11) not null default '0',
owner_tbl int(11) default null,
owner_id int(11) default null,
sla_id int(11) default null,
inc_web int(11) default null,
inc_email int(11) default null,
inc_chat int(11) default null,
inc_csr int(11) default null,
inc_total int(11) default null,
time_billed int(11) default null,
activedate timestamp null default null,
expiredate timestamp null default null,
state int(11) default null,
sla_set int(11) default null,
unique key t2$slai_id (slai_id),
key t2$owner_id (owner_id),
key t2$sla_id (sla_id)
) engine=innodb;
insert into t2(slai_id, owner_tbl, owner_id, sla_id) values
(1,3,1,1), (3,3,10,2), (4,3,3,6), (5,3,2,5), (6,3,8,3), (7,3,9,7),
(8,3,6,8), (9,3,4,9), (10,3,5,10), (11,3,11,11), (12,3,7,12);
flush tables;
select si.slai_id
from t1 c join t2 si on
((si.owner_tbl = 3 and si.owner_id = c.org_id) or
( si.owner_tbl = 2 and si.owner_id = c.c_id))
where
c.c_id = 218 and expiredate is null;
slai_id
12
select * from t1 where org_id is null;
c_id org_id
2 NULL
120 NULL
141 NULL
select si.slai_id
from t1 c join t2 si on
((si.owner_tbl = 3 and si.owner_id = c.org_id) or
( si.owner_tbl = 2 and si.owner_id = c.c_id))
where
c.c_id = 218 and expiredate is null;
slai_id
12
drop table t1, t2;
create table t1m (a int) engine=myisam;
create table t1i (a int) engine=innodb;
create table t2m (a int) engine=myisam;
create table t2i (a int) engine=innodb;
insert into t2m values (5);
insert into t2i values (5);
select min(a) from t1m;
min(a)
NULL
select min(7) from t1m;
min(7)
NULL
select min(7) from DUAL;
min(7)
NULL
explain select min(7) from t2m join t1m;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select min(7) from t2m join t1m;
min(7)
NULL
select max(a) from t1m;
max(a)
NULL
select max(7) from t1m;
max(7)
NULL
select max(7) from DUAL;
max(7)
NULL
explain select max(7) from t2m join t1m;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select max(7) from t2m join t1m;
max(7)
NULL
select 1, min(a) from t1m where a=99;
1 min(a)
1 NULL
select 1, min(a) from t1m where 1=99;
1 min(a)
1 NULL
select 1, min(1) from t1m where a=99;
1 min(1)
1 NULL
select 1, min(1) from t1m where 1=99;
1 min(1)
1 NULL
select 1, max(a) from t1m where a=99;
1 max(a)
1 NULL
select 1, max(a) from t1m where 1=99;
1 max(a)
1 NULL
select 1, max(1) from t1m where a=99;
1 max(1)
1 NULL
select 1, max(1) from t1m where 1=99;
1 max(1)
1 NULL
select min(a) from t1i;
min(a)
NULL
select min(7) from t1i;
min(7)
NULL
select min(7) from DUAL;
min(7)
NULL
explain select min(7) from t2i join t1i;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2i ALL NULL NULL NULL NULL 1
1 SIMPLE t1i ALL NULL NULL NULL NULL 1
select min(7) from t2i join t1i;
min(7)
NULL
select max(a) from t1i;
max(a)
NULL
select max(7) from t1i;
max(7)
NULL
select max(7) from DUAL;
max(7)
NULL
explain select max(7) from t2i join t1i;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2i ALL NULL NULL NULL NULL 1
1 SIMPLE t1i ALL NULL NULL NULL NULL 1
select max(7) from t2i join t1i;
max(7)
NULL
select 1, min(a) from t1i where a=99;
1 min(a)
1 NULL
select 1, min(a) from t1i where 1=99;
1 min(a)
1 NULL
select 1, min(1) from t1i where a=99;
1 min(1)
1 NULL
select 1, min(1) from t1i where 1=99;
1 min(1)
1 NULL
select 1, max(a) from t1i where a=99;
1 max(a)
1 NULL
select 1, max(a) from t1i where 1=99;
1 max(a)
1 NULL
select 1, max(1) from t1i where a=99;
1 max(1)
1 NULL
select 1, max(1) from t1i where 1=99;
1 max(1)
1 NULL
explain select count(*), min(7), max(7) from t1m, t1i;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1m system NULL NULL NULL NULL 0 const row not found
1 SIMPLE t1i ALL NULL NULL NULL NULL 1
select count(*), min(7), max(7) from t1m, t1i;
count(*) min(7) max(7)
0 NULL NULL
explain select count(*), min(7), max(7) from t1m, t2i;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1m system NULL NULL NULL NULL 0 const row not found
1 SIMPLE t2i ALL NULL NULL NULL NULL 1
select count(*), min(7), max(7) from t1m, t2i;
count(*) min(7) max(7)
0 NULL NULL
explain select count(*), min(7), max(7) from t2m, t1i;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2m system NULL NULL NULL NULL 1
1 SIMPLE t1i ALL NULL NULL NULL NULL 1
select count(*), min(7), max(7) from t2m, t1i;
count(*) min(7) max(7)
0 NULL NULL
drop table t1m, t1i, t2m, t2i;
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