create unique index multiple columns with one is columns value is zero
0
I have a table users with following columns and attributes
users (
id int(11),
ssn varchar(100),
foreigner tinyint(1) default 0
)
foreigner values is 0 and 1 default 0
how I can create unique index on column ssn, when checked foreigner value is 0.
id ssn foreigner
1 55 0 true
2 60 1 true
3 60 1 true
----------------------------------
4 55 0 false
----------------------------------
5 77 0 true
mysql sql database
edited Nov 15 '18 at 12:23
Raza Rafaideen
5381518
asked Nov 15 '18 at 11:43
Meqenaneri VacharqMeqenaneri Vacharq
217
add a comment |
0
I have a table users with following columns and attributes
users (
id int(11),
ssn varchar(100),
foreigner tinyint(1) default 0
)
foreigner values is 0 and 1 default 0
how I can create unique index on column ssn, when checked foreigner value is 0.
id ssn foreigner
1 55 0 true
2 60 1 true
3 60 1 true
----------------------------------
4 55 0 false
----------------------------------
5 77 0 true
mysql sql database
edited Nov 15 '18 at 12:23
Raza Rafaideen
5381518
asked Nov 15 '18 at 11:43
Meqenaneri VacharqMeqenaneri Vacharq
217
Can there be multiple rows possible with (55,1) ?
– Madhur Bhaiya
Nov 15 '18 at 11:44
add a comment |
0
0
0
0
I have a table users with following columns and attributes
users (
id int(11),
ssn varchar(100),
foreigner tinyint(1) default 0
)
foreigner values is 0 and 1 default 0
how I can create unique index on column ssn, when checked foreigner value is 0.
id ssn foreigner
1 55 0 true
2 60 1 true
3 60 1 true
----------------------------------
4 55 0 false
----------------------------------
5 77 0 true
mysql sql database
edited Nov 15 '18 at 12:23
Raza Rafaideen
5381518
asked Nov 15 '18 at 11:43
Meqenaneri VacharqMeqenaneri Vacharq
217
I have a table users with following columns and attributes
users (
id int(11),
ssn varchar(100),
foreigner tinyint(1) default 0
)
foreigner values is 0 and 1 default 0
how I can create unique index on column ssn, when checked foreigner value is 0.
id ssn foreigner
1 55 0 true
2 60 1 true
3 60 1 true
----------------------------------
4 55 0 false
----------------------------------
5 77 0 true
mysql sql database
mysql sql database
edited Nov 15 '18 at 12:23
Raza Rafaideen
5381518
asked Nov 15 '18 at 11:43
Meqenaneri VacharqMeqenaneri Vacharq
217
edited Nov 15 '18 at 12:23
Raza Rafaideen
5381518
asked Nov 15 '18 at 11:43
Meqenaneri VacharqMeqenaneri Vacharq
217
edited Nov 15 '18 at 12:23
Raza Rafaideen
5381518
edited Nov 15 '18 at 12:23
Raza Rafaideen
5381518
edited Nov 15 '18 at 12:23
Raza Rafaideen
5381518
5381518
asked Nov 15 '18 at 11:43
Meqenaneri VacharqMeqenaneri Vacharq
217
asked Nov 15 '18 at 11:43
Meqenaneri VacharqMeqenaneri Vacharq
217
asked Nov 15 '18 at 11:43
Meqenaneri VacharqMeqenaneri Vacharq
217
217
Can there be multiple rows possible with (55,1) ?
– Madhur Bhaiya
Nov 15 '18 at 11:44
add a comment |
Can there be multiple rows possible with (55,1) ?
– Madhur Bhaiya
Nov 15 '18 at 11:44
Can there be multiple rows possible with (55,1) ?
– Madhur Bhaiya
Nov 15 '18 at 11:44
Can there be multiple rows possible with (55,1) ?
– Madhur Bhaiya
Nov 15 '18 at 11:44
add a comment |
1 Answer
1
active
oldest
votes
1
You can only do this without a trigger in MySQL using the most recent versions of MySQL.
create table users (
id int(11),
ssn varchar(100),
foreigner tinyint(1) default 0,
foreigner_ssn tinyint generated always as (case when foreigner = 0 then ssn end) store unique
);
This creates a new generated column. MySQL unique indexes to repeat NULL values, so the condition is really only on foreigner = 0.
You could possibly simplify this, just by having ssn be NULL when foreigner = 0 and declaring that to be unique.
answered Nov 15 '18 at 11:50
Gordon LinoffGordon Linoff
766k35300402
topicstarter and or future readers but keep in mind this query only works on a InnoDB table engine which supports indexing on virtaul columns like this.. MyISAM only supports it when you use stored see demos InnoDB db-fiddle.com/f/5EFMpZn1czkM5rM8rJPb3V/1 and MyISAM db-fiddle.com/f/5EFMpZn1czkM5rM8rJPb3V/0 .. But who is using MyISAM nowadays all modern MySQL versions run InnoDB table engine as default now..
– Raymond Nijland
Nov 15 '18 at 12:20
thank you for your response. I am using 5.5.56-MariaDB
– Meqenaneri Vacharq
Nov 15 '18 at 12:29
[Err] 1904 - Key/Index cannot be defined on a non-stored computed column
– Meqenaneri Vacharq
Nov 15 '18 at 13:05
@MeqenaneriVacharq . . . So store the value (thestorekeyword). I wasn't sure if that would be necessary.
– Gordon Linoff
Nov 15 '18 at 13:24
add a comment |
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1 Answer
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active
oldest
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1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
1
You can only do this without a trigger in MySQL using the most recent versions of MySQL.
create table users (
id int(11),
ssn varchar(100),
foreigner tinyint(1) default 0,
foreigner_ssn tinyint generated always as (case when foreigner = 0 then ssn end) store unique
);
This creates a new generated column. MySQL unique indexes to repeat NULL values, so the condition is really only on foreigner = 0.
You could possibly simplify this, just by having ssn be NULL when foreigner = 0 and declaring that to be unique.
answered Nov 15 '18 at 11:50
Gordon LinoffGordon Linoff
766k35300402
topicstarter and or future readers but keep in mind this query only works on a InnoDB table engine which supports indexing on virtaul columns like this.. MyISAM only supports it when you use stored see demos InnoDB db-fiddle.com/f/5EFMpZn1czkM5rM8rJPb3V/1 and MyISAM db-fiddle.com/f/5EFMpZn1czkM5rM8rJPb3V/0 .. But who is using MyISAM nowadays all modern MySQL versions run InnoDB table engine as default now..
– Raymond Nijland
Nov 15 '18 at 12:20
thank you for your response. I am using 5.5.56-MariaDB
– Meqenaneri Vacharq
Nov 15 '18 at 12:29
[Err] 1904 - Key/Index cannot be defined on a non-stored computed column
– Meqenaneri Vacharq
Nov 15 '18 at 13:05
@MeqenaneriVacharq . . . So store the value (thestorekeyword). I wasn't sure if that would be necessary.
– Gordon Linoff
Nov 15 '18 at 13:24
add a comment |
1
You can only do this without a trigger in MySQL using the most recent versions of MySQL.
create table users (
id int(11),
ssn varchar(100),
foreigner tinyint(1) default 0,
foreigner_ssn tinyint generated always as (case when foreigner = 0 then ssn end) store unique
);
This creates a new generated column. MySQL unique indexes to repeat NULL values, so the condition is really only on foreigner = 0.
You could possibly simplify this, just by having ssn be NULL when foreigner = 0 and declaring that to be unique.
answered Nov 15 '18 at 11:50
Gordon LinoffGordon Linoff
766k35300402
topicstarter and or future readers but keep in mind this query only works on a InnoDB table engine which supports indexing on virtaul columns like this.. MyISAM only supports it when you use stored see demos InnoDB db-fiddle.com/f/5EFMpZn1czkM5rM8rJPb3V/1 and MyISAM db-fiddle.com/f/5EFMpZn1czkM5rM8rJPb3V/0 .. But who is using MyISAM nowadays all modern MySQL versions run InnoDB table engine as default now..
– Raymond Nijland
Nov 15 '18 at 12:20
thank you for your response. I am using 5.5.56-MariaDB
– Meqenaneri Vacharq
Nov 15 '18 at 12:29
[Err] 1904 - Key/Index cannot be defined on a non-stored computed column
– Meqenaneri Vacharq
Nov 15 '18 at 13:05
@MeqenaneriVacharq . . . So store the value (thestorekeyword). I wasn't sure if that would be necessary.
– Gordon Linoff
Nov 15 '18 at 13:24
add a comment |
1
1
1
You can only do this without a trigger in MySQL using the most recent versions of MySQL.
create table users (
id int(11),
ssn varchar(100),
foreigner tinyint(1) default 0,
foreigner_ssn tinyint generated always as (case when foreigner = 0 then ssn end) store unique
);
This creates a new generated column. MySQL unique indexes to repeat NULL values, so the condition is really only on foreigner = 0.
You could possibly simplify this, just by having ssn be NULL when foreigner = 0 and declaring that to be unique.
answered Nov 15 '18 at 11:50
Gordon LinoffGordon Linoff
766k35300402
You can only do this without a trigger in MySQL using the most recent versions of MySQL.
create table users (
id int(11),
ssn varchar(100),
foreigner tinyint(1) default 0,
foreigner_ssn tinyint generated always as (case when foreigner = 0 then ssn end) store unique
);
This creates a new generated column. MySQL unique indexes to repeat NULL values, so the condition is really only on foreigner = 0.
You could possibly simplify this, just by having ssn be NULL when foreigner = 0 and declaring that to be unique.
answered Nov 15 '18 at 11:50
Gordon LinoffGordon Linoff
766k35300402
edited Nov 15 '18 at 13:24
answered Nov 15 '18 at 11:50
Gordon LinoffGordon Linoff
766k35300402
answered Nov 15 '18 at 11:50
Gordon LinoffGordon Linoff
766k35300402
answered Nov 15 '18 at 11:50
Gordon LinoffGordon Linoff
766k35300402
766k35300402
topicstarter and or future readers but keep in mind this query only works on a InnoDB table engine which supports indexing on virtaul columns like this.. MyISAM only supports it when you use stored see demos InnoDB db-fiddle.com/f/5EFMpZn1czkM5rM8rJPb3V/1 and MyISAM db-fiddle.com/f/5EFMpZn1czkM5rM8rJPb3V/0 .. But who is using MyISAM nowadays all modern MySQL versions run InnoDB table engine as default now..
– Raymond Nijland
Nov 15 '18 at 12:20
thank you for your response. I am using 5.5.56-MariaDB
– Meqenaneri Vacharq
Nov 15 '18 at 12:29
[Err] 1904 - Key/Index cannot be defined on a non-stored computed column
– Meqenaneri Vacharq
Nov 15 '18 at 13:05
@MeqenaneriVacharq . . . So store the value (thestorekeyword). I wasn't sure if that would be necessary.
– Gordon Linoff
Nov 15 '18 at 13:24
add a comment |
topicstarter and or future readers but keep in mind this query only works on a InnoDB table engine which supports indexing on virtaul columns like this.. MyISAM only supports it when you use stored see demos InnoDB db-fiddle.com/f/5EFMpZn1czkM5rM8rJPb3V/1 and MyISAM db-fiddle.com/f/5EFMpZn1czkM5rM8rJPb3V/0 .. But who is using MyISAM nowadays all modern MySQL versions run InnoDB table engine as default now..
– Raymond Nijland
Nov 15 '18 at 12:20
thank you for your response. I am using 5.5.56-MariaDB
– Meqenaneri Vacharq
Nov 15 '18 at 12:29
[Err] 1904 - Key/Index cannot be defined on a non-stored computed column
– Meqenaneri Vacharq
Nov 15 '18 at 13:05
@MeqenaneriVacharq . . . So store the value (thestorekeyword). I wasn't sure if that would be necessary.
– Gordon Linoff
Nov 15 '18 at 13:24
topicstarter and or future readers but keep in mind this query only works on a InnoDB table engine which supports indexing on virtaul columns like this.. MyISAM only supports it when you use stored see demos InnoDB db-fiddle.com/f/5EFMpZn1czkM5rM8rJPb3V/1 and MyISAM db-fiddle.com/f/5EFMpZn1czkM5rM8rJPb3V/0 .. But who is using MyISAM nowadays all modern MySQL versions run InnoDB table engine as default now..
– Raymond Nijland
Nov 15 '18 at 12:20
topicstarter and or future readers but keep in mind this query only works on a InnoDB table engine which supports indexing on virtaul columns like this.. MyISAM only supports it when you use stored see demos InnoDB db-fiddle.com/f/5EFMpZn1czkM5rM8rJPb3V/1 and MyISAM db-fiddle.com/f/5EFMpZn1czkM5rM8rJPb3V/0 .. But who is using MyISAM nowadays all modern MySQL versions run InnoDB table engine as default now..
– Raymond Nijland
Nov 15 '18 at 12:20
thank you for your response. I am using 5.5.56-MariaDB
– Meqenaneri Vacharq
Nov 15 '18 at 12:29
thank you for your response. I am using 5.5.56-MariaDB
– Meqenaneri Vacharq
Nov 15 '18 at 12:29
[Err] 1904 - Key/Index cannot be defined on a non-stored computed column
– Meqenaneri Vacharq
Nov 15 '18 at 13:05
[Err] 1904 - Key/Index cannot be defined on a non-stored computed column
– Meqenaneri Vacharq
Nov 15 '18 at 13:05
@MeqenaneriVacharq . . . So store the value (the
store keyword). I wasn't sure if that would be necessary.– Gordon Linoff
Nov 15 '18 at 13:24
@MeqenaneriVacharq . . . So store the value (the
store keyword). I wasn't sure if that would be necessary.– Gordon Linoff
Nov 15 '18 at 13:24
add a comment |
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Can there be multiple rows possible with (55,1) ?
– Madhur Bhaiya
Nov 15 '18 at 11:44