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1. When mixing NULL to a character string,

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the result takes its charset/collation
attributes from the character string,
e.g.  SELECT func(NULL, _latin2'string')
now returns a latin2 result. This is
done by introducing a new derivation
(aka coercibility) level DERIVATION_IGNORABLE,
which is used with Item_null.
2. 'Pure' NULL is now BINARY(0), not CHAR(0).
I.e. NULL is now more typeless.
This commit is contained in:
bar@mysql.com
2004-11-10 14:05:28 +04:00
parent 2f50044794
commit c51d7acfcc
11 changed files with 181 additions and 17 deletions
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94
mysql-test/r/null.result
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@ -175,3 +175,97 @@ explain select * from t1 where i=2 or i is null;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref i i 4 const 7 Using where; Using index
drop table t1;
set names latin2;
create table t1 select
null as c00,
if(1, null, 'string') as c01,
if(0, null, 'string') as c02,
ifnull(null, 'string') as c03,
ifnull('string', null) as c04,
case when 0 then null else 'string' end as c05,
case when 1 then null else 'string' end as c06,
coalesce(null, 'string') as c07,
coalesce('string', null) as c08,
least('string',null) as c09,
least(null, 'string') as c10,
greatest('string',null) as c11,
greatest(null, 'string') as c12,
nullif('string', null) as c13,
nullif(null, 'string') as c14,
trim('string' from null) as c15,
trim(null from 'string') as c16,
substring_index('string', null, 1) as c17,
substring_index(null, 'string', 1) as c18,
elt(1, null, 'string') as c19,
elt(1, 'string', null) as c20,
concat('string', null) as c21,
concat(null, 'string') as c22,
concat_ws('sep', 'string', null) as c23,
concat_ws('sep', null, 'string') as c24,
concat_ws(null, 'string', 'string') as c25,
make_set(3, 'string', null) as c26,
make_set(3, null, 'string') as c27,
export_set(3, null, 'off', 'sep') as c29,
export_set(3, 'on', null, 'sep') as c30,
export_set(3, 'on', 'off', null) as c31,
replace(null, 'from', 'to') as c32,
replace('str', null, 'to') as c33,
replace('str', 'from', null) as c34,
insert('str', 1, 2, null) as c35,
insert(null, 1, 2, 'str') as c36,
lpad('str', 10, null) as c37,
rpad(null, 10, 'str') as c38;
show create table t1;
Table Create Table
t1 CREATE TABLE `t1` (
`c00` binary(0) default NULL,
`c01` varchar(6) character set latin2 default NULL,
`c02` varchar(6) character set latin2 default NULL,
`c03` varchar(6) character set latin2 NOT NULL default '',
`c04` varchar(6) character set latin2 default NULL,
`c05` varchar(6) character set latin2 default NULL,
`c06` varchar(6) character set latin2 default NULL,
`c07` varchar(6) character set latin2 default NULL,
`c08` varchar(6) character set latin2 default NULL,
`c09` varchar(6) character set latin2 NOT NULL default '',
`c10` varchar(6) character set latin2 NOT NULL default '',
`c11` varchar(6) character set latin2 NOT NULL default '',
`c12` varchar(6) character set latin2 NOT NULL default '',
`c13` varchar(6) character set latin2 default NULL,
`c14` char(0) character set latin2 default NULL,
`c15` char(0) character set latin2 default NULL,
`c16` varchar(6) character set latin2 default NULL,
`c17` varchar(6) character set latin2 default NULL,
`c18` char(0) character set latin2 default NULL,
`c19` varchar(6) character set latin2 default NULL,
`c20` varchar(6) character set latin2 default NULL,
`c21` varchar(6) character set latin2 default NULL,
`c22` varchar(6) character set latin2 default NULL,
`c23` varchar(9) character set latin2 default NULL,
`c24` varchar(9) character set latin2 default NULL,
`c25` varchar(12) character set latin2 default NULL,
`c26` varchar(7) character set latin2 default NULL,
`c27` varchar(7) character set latin2 default NULL,
`c29` longtext character set latin2,
`c30` longtext character set latin2,
`c31` varchar(192) character set latin2 default NULL,
`c32` char(0) character set latin2 default NULL,
`c33` char(3) character set latin2 default NULL,
`c34` char(3) character set latin2 default NULL,
`c35` char(3) character set latin2 default NULL,
`c36` char(3) character set latin2 default NULL,
`c37` varchar(10) character set latin2 default NULL,
`c38` varchar(10) character set latin2 default NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1
drop table t1;
select
case 'str' when 'STR' then 'str' when null then 'null' end as c01,
case 'str' when null then 'null' when 'STR' then 'str' end as c02,
field(null, 'str1', 'str2') as c03,
field('str1','STR1', null) as c04,
field('str1', null, 'STR1') as c05,
'string' in ('STRING', null) as c08,
'string' in (null, 'STRING') as c09;
c01 c02 c03 c04 c05 c08 c09
str str 0 1 2 1 1
set names latin1;