{"Entry":{"collection":"type","key":"enums","name":"Enumerated types","aliases":[],"metadata":{"aliases":[],"category":"Type families","content_hash":"ee2e64dd1ee6af145f35e73be2608fb60b10f3c2e0f2911b649ce8f12f570aa9","imported_at":"2026-09-30T00:40:35.706357+08:00","name":"Enumerated types","name_zh":"","slug":"enums","summary":"Enumerated (enum) types are data types that comprise a static, ordered set of values. They are equivalent to the enum types supported in a number of programming languages. An example of an enum type might be the days of the week, or a set of status values for a piece of data."}},"Definition":{"Collection":"type","Key":"enums","SourceDatabase":"center","Version":"18","SourceTable":"data_type","SourceKey":"enums","SourceRevision":"555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f","Facts":{"aliases":[],"casts":[],"catalog":{},"coverage":"documented type family or SQL syntax; not a catalog object","description":["Enumerated (enum) types are data types that comprise a static, ordered set of values. They are equivalent to the enum types supported in a number of programming languages. An example of an enum type might be the days of the week, or a set of status values for a piece of data."],"facts":[{"label":"Object boundary","value":"User-defined type family; not a finite list of user objects"}],"manual_html":"\u003cdiv class=\"sect1\" id=\"DATATYPE-ENUM\"\u003e\n\u003cdiv class=\"titlepage\"\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003ch2 class=\"title\"\u003e8.7. Enumerated Types \u003c/h2\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\n\u003cp\u003eEnumerated (enum) types are data types that comprise a static, ordered set of values. They are equivalent to the \u003ccode class=\"type\"\u003eenum\u003c/code\u003e types supported in a number of programming languages. An example of an enum type might be the days of the week, or a set of status values for a piece of data.\u003c/p\u003e\n\u003cdiv class=\"sect2\" id=\"DATATYPE-ENUM-DECLARATION\"\u003e\n\u003cdiv class=\"titlepage\"\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003ch3 class=\"title\"\u003e8.7.1. Declaration of Enumerated Types \u003c/h3\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eEnum types are created using the \u003ca class=\"xref\" href=\"/docs/18/sql-createtype.html\" title=\"CREATE TYPE\"\u003e\u003cspan class=\"refentrytitle\"\u003eCREATE TYPE\u003c/span\u003e\u003c/a\u003e command, for example:\u003c/p\u003e\n\u003cpre class=\"programlisting\"\u003eCREATE TYPE mood AS ENUM ('sad', 'ok', 'happy');\n\u003c/pre\u003e\n\u003cp\u003eOnce created, the enum type can be used in table and function definitions much like any other type:\u003c/p\u003e\n\u003cpre class=\"programlisting\"\u003eCREATE TYPE mood AS ENUM ('sad', 'ok', 'happy');\nCREATE TABLE person (\n    name text,\n    current_mood mood\n);\nINSERT INTO person VALUES ('Moe', 'happy');\nSELECT * FROM person WHERE current_mood = 'happy';\n name | current_mood\n------+--------------\n Moe  | happy\n(1 row)\n\u003c/pre\u003e\n\u003c/div\u003e\n\u003cdiv class=\"sect2\" id=\"DATATYPE-ENUM-ORDERING\"\u003e\n\u003cdiv class=\"titlepage\"\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003ch3 class=\"title\"\u003e8.7.2. Ordering \u003c/h3\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eThe ordering of the values in an enum type is the order in which the values were listed when the type was created. All standard comparison operators and related aggregate functions are supported for enums. For example:\u003c/p\u003e\n\u003cpre class=\"programlisting\"\u003eINSERT INTO person VALUES ('Larry', 'sad');\nINSERT INTO person VALUES ('Curly', 'ok');\nSELECT * FROM person WHERE current_mood \u0026gt; 'sad';\n name  | current_mood\n-------+--------------\n Moe   | happy\n Curly | ok\n(2 rows)\n\nSELECT * FROM person WHERE current_mood \u0026gt; 'sad' ORDER BY current_mood;\n name  | current_mood\n-------+--------------\n Curly | ok\n Moe   | happy\n(2 rows)\n\nSELECT name\nFROM person\nWHERE current_mood = (SELECT MIN(current_mood) FROM person);\n name\n-------\n Larry\n(1 row)\n\u003c/pre\u003e\n\u003c/div\u003e\n\u003cdiv class=\"sect2\" id=\"DATATYPE-ENUM-TYPE-SAFETY\"\u003e\n\u003cdiv class=\"titlepage\"\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003ch3 class=\"title\"\u003e8.7.3. Type Safety \u003c/h3\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eEach enumerated data type is separate and cannot be compared with other enumerated types. See this example:\u003c/p\u003e\n\u003cpre class=\"programlisting\"\u003eCREATE TYPE happiness AS ENUM ('happy', 'very happy', 'ecstatic');\nCREATE TABLE holidays (\n    num_weeks integer,\n    happiness happiness\n);\nINSERT INTO holidays(num_weeks,happiness) VALUES (4, 'happy');\nINSERT INTO holidays(num_weeks,happiness) VALUES (6, 'very happy');\nINSERT INTO holidays(num_weeks,happiness) VALUES (8, 'ecstatic');\nINSERT INTO holidays(num_weeks,happiness) VALUES (2, 'sad');\nERROR:  invalid input value for enum happiness: \"sad\"\nSELECT person.name, holidays.num_weeks FROM person, holidays\n  WHERE person.current_mood = holidays.happiness;\nERROR:  operator does not exist: mood = happiness\n\u003c/pre\u003e\n\u003cp\u003eIf you really need to do something like that, you can either write a custom operator or add explicit casts to your query:\u003c/p\u003e\n\u003cpre class=\"programlisting\"\u003eSELECT person.name, holidays.num_weeks FROM person, holidays\n  WHERE person.current_mood::text = holidays.happiness::text;\n name | num_weeks\n------+-----------\n Moe  |         4\n(1 row)\n\n\u003c/pre\u003e\n\u003c/div\u003e\n\u003cdiv class=\"sect2\" id=\"DATATYPE-ENUM-IMPLEMENTATION-DETAILS\"\u003e\n\u003cdiv class=\"titlepage\"\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003ch3 class=\"title\"\u003e8.7.4. Implementation Details \u003c/h3\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eEnum labels are case sensitive, so \u003ccode class=\"type\"\u003e'happy'\u003c/code\u003e is not the same as \u003ccode class=\"type\"\u003e'HAPPY'\u003c/code\u003e. White space in the labels is significant too.\u003c/p\u003e\n\u003cp\u003eAlthough enum types are primarily intended for static sets of values, there is support for adding new values to an existing enum type, and for renaming values (see \u003ca class=\"xref\" href=\"/docs/18/sql-altertype.html\" title=\"ALTER TYPE\"\u003e\u003cspan class=\"refentrytitle\"\u003eALTER TYPE\u003c/span\u003e\u003c/a\u003e). Existing values cannot be removed from an enum type, nor can the sort ordering of such values be changed, short of dropping and re-creating the enum type.\u003c/p\u003e\n\u003cp\u003eAn enum value occupies four bytes on disk. The length of an enum value's textual label is limited by the \u003ccode class=\"symbol\"\u003eNAMEDATALEN\u003c/code\u003e setting compiled into \u003cspan class=\"productname\"\u003ePostgreSQL\u003c/span\u003e; in standard builds this means at most 63 bytes.\u003c/p\u003e\n\u003cp\u003eThe translations from internal enum values to textual labels are kept in the system catalog \u003ca class=\"link\" href=\"/docs/18/catalog-pg-enum.html\" title=\"52.20. pg_enum\"\u003e\u003ccode class=\"structname\"\u003epg_enum\u003c/code\u003e\u003c/a\u003e. Querying this catalog directly can be useful.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/div\u003e","manual_path":"datatype-enum.html","operator_classes":[],"operators":[],"ranges":[],"related":[],"release":{"channel":"stable","label":"18.6","major":"18","manual_sha256":{"arrays.html":"0e1d5c5a7b4a949d4439995f44f74ad4264e050d16eb9ad2a850fbaee04032df","catalog-pg-type.html":"ea9c9313bab8e92a7da18ebc50c7ff1f908dd80999a7e0ca3bbc82ba626c58d4","datatype-binary.html":"0c03ec47b76e37888a3da7f5dcfd340128a5d356642a85185cc9ebe17856a904","datatype-bit.html":"c49124aad561636c18080b9e09572fde7785a6b9eae86f5a33283f0fd6774c37","datatype-boolean.html":"b633f663e6c8276e7056287640c413aa79dbc15d5353cee0d41653d58d376956","datatype-character.html":"c73eebe413ea709a7792e4cfc3cfe9fb68cb496ebe83c3ebaa9d09f8c40d0f73","datatype-datetime.html":"e366275d8b13845bfa4ef0d68faa093e5f3ecb708a1ec870cbcbf7e425b85699","datatype-enum.html":"cab38e53222e30cc94b24de4b33634fd22d7c93f58ebcf35f646c9b8da78fae8","datatype-geometric.html":"0eb3053cfe7d6b0a4b5592c5d7af8d97cae527e87f063c5793413bcba5c14cd9","datatype-json.html":"650162a05b660146b500a205d523374d00aee117a6a6240d30262be51b6e33e5","datatype-money.html":"8b29c14b90679683ac5c472b59a0a7e2853f32cc7db43fab417b2697a6879964","datatype-net-types.html":"96846e641cc37727ddcd8b8a1aa0dbe33cd9787760a2b4efb0dcb9403d5be63f","datatype-numeric.html":"b74619f7ac2f1ca9f85c48073df78c33dd30e464e61baba6008634534edcb500","datatype-oid.html":"8b3360302225f08ae72716ce1804596de95b568e5d31f788cb4597427b28cc38","datatype-pg-lsn.html":"339172f5107cc7eb7139bec911277647219e92a532cebd0f3da0a5dacf8195af","datatype-pseudo.html":"c7cf0b8214304bd8702c95f2142671ae5f0d631f83717f9c07d9e1f2579961b4","datatype-textsearch.html":"4b15e05be8b49a71b28aea22f2c46d0dbf639a91e7b4fe129a4c737c6daad47c","datatype-uuid.html":"292b307b3223c6182bdba687e7f69e6dca9038430143ad79d56327f6ed4c3246","datatype-xml.html":"061fc2295b7b69be704f0a741b8decd10ad721059f871fb0243c669bb54d7822","datatype.html":"e581f67c74e42006289638c8659e9b338adbfd7f068bd8bf2b3be3880fcd2254","domains.html":"82d486973ccc35d14276627a67ac76b434452f23f9ed4d8aa3fbb01fdf285fc2","functions-info.html":"78ac80bf81da2e4f4a33f3b850faa86f0f58ec54a083d6c31da557907de0df87","rangetypes.html":"e4960abc7ce8e51d794f94f1e57b099d30b7f75dd7f2b23a960eef91f6291c33","rowtypes.html":"74f99e029c3a9edfd3e18810ba3c8cb66d3aada91eb67b86476560871e6617e9","sql-createdomain.html":"e94f927196de1b0ea1ce35cd4603c1f6f544439adcc0edf1c4222358e832245b"},"ref":"https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2","revision":"555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f","source_files":{"doc/src/sgml/datatype.sgml":"86328daa77e20d81d222376ec0306d9841a17104e436c08d138eb763aefb3700","src/include/catalog/pg_am.dat":"b3cb86b102a42fb0024cbd99779c9897afb40d12a71f5cc5a0e5aee7ff2f9969","src/include/catalog/pg_am.h":"3426799df799f32163fcc0765f43dbdb5e88e626acf31284fef9fc6014b69d8e","src/include/catalog/pg_cast.dat":"97911281ca2c81917394ccb2ec13367e37c6801fd461d5e1a3d2f28b911b46b2","src/include/catalog/pg_cast.h":"de585c7df687d698e7d1d100dce8a794ac9da52414ea48169191019178c8f053","src/include/catalog/pg_opclass.dat":"4ee7d3619a6aa106e1c0db55de903931c7d11b1c60ba053a022519c55f8ee668","src/include/catalog/pg_opclass.h":"9c218537806c8ef0398302faaca7f91315dfc1198c48706cebffb479b68defaf","src/include/catalog/pg_operator.dat":"5d35b9b2ef5f9797cc815263927ef8a12367fedace53e828b4e8b320e2a7f703","src/include/catalog/pg_operator.h":"621b18cfffe102413d79b746ce7a10f77fc60fdd097bac34c22b31070d3ee3c4","src/include/catalog/pg_opfamily.dat":"3b694879027b858f2ecf1fa1152b7e30c6e15a216ba99c2384291c30e9d52311","src/include/catalog/pg_opfamily.h":"e1f5fc8aebd3042df847455bf66bf755f768c2aa8a9b03d22f7ec8563eba59c0","src/include/catalog/pg_proc.dat":"1f934ce80d460159dda137714374a35f9896315ea2476709cbb4da13b38ef95a","src/include/catalog/pg_proc.h":"f7d59f07c5b95e2f3c7141762a0f576e8a3af7581ba54c27537f4d500472bea5","src/include/catalog/pg_range.dat":"5c2271f8e89e9378d1887204e5785060b77405b5f0ff3e6c719250c9c1dcfcc4","src/include/catalog/pg_range.h":"45546d952b5181f989bd9234721897fc2b37005c8e49ce2ddc156f26974c3ca4","src/include/catalog/pg_type.dat":"5f5887b75677cba2d4a1a0cfeb355df5ed91f85d385fac88bd8d7c605b3578f9","src/include/catalog/pg_type.h":"8fb198749fd82b6c1818a3c18455f226f66116fcfeb3d4959c65ce3fda22802e"},"source_sha256":"555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"},"sections":[],"signature":"Enumerated 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18 English manual","path":"datatype-enum.html","sha256":"cab38e53222e30cc94b24de4b33634fd22d7c93f58ebcf35f646c9b8da78fae8","url":"/docs/18/datatype-enum.html"}]},"MeasuredEvidence":{}},"Text":{"Collection":"type","Key":"enums","SourceDatabase":"center","Version":"18","Locale":"en","Title":"Enumerated types","Summary":"Enumerated (enum) types are data types that comprise a static, ordered set of values. They are equivalent to the enum types supported in a number of programming languages. An example of an enum type might be the days of the week, or a set of status values for a piece of data.","BodyHTML":"\u003cdiv id=\"DATATYPE-ENUM\"\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003ch2\u003e8.7. Enumerated Types \u003c/h2\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\n\u003cp\u003eEnumerated (enum) types are data types that comprise a static, ordered set of values. They are equivalent to the \u003ccode\u003eenum\u003c/code\u003e types supported in a number of programming languages. An example of an enum type might be the days of the week, or a set of status values for a piece of data.\u003c/p\u003e\n\u003cdiv id=\"DATATYPE-ENUM-DECLARATION\"\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003ch3\u003e8.7.1. Declaration of Enumerated Types \u003c/h3\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eEnum types are created using the \u003ca href=\"/docs/18/sql-createtype.html\" title=\"CREATE TYPE\" rel=\"nofollow\"\u003e\u003cspan\u003eCREATE TYPE\u003c/span\u003e\u003c/a\u003e command, for example:\u003c/p\u003e\n\u003cpre\u003eCREATE TYPE mood AS ENUM (\u0026#39;sad\u0026#39;, \u0026#39;ok\u0026#39;, \u0026#39;happy\u0026#39;);\n\u003c/pre\u003e\n\u003cp\u003eOnce created, the enum type can be used in table and function definitions much like any other type:\u003c/p\u003e\n\u003cpre\u003eCREATE TYPE mood AS ENUM (\u0026#39;sad\u0026#39;, \u0026#39;ok\u0026#39;, \u0026#39;happy\u0026#39;);\nCREATE TABLE person (\n    name text,\n    current_mood mood\n);\nINSERT INTO person VALUES (\u0026#39;Moe\u0026#39;, \u0026#39;happy\u0026#39;);\nSELECT * FROM person WHERE current_mood = \u0026#39;happy\u0026#39;;\n name | current_mood\n------+--------------\n Moe  | happy\n(1 row)\n\u003c/pre\u003e\n\u003c/div\u003e\n\u003cdiv id=\"DATATYPE-ENUM-ORDERING\"\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003ch3\u003e8.7.2. Ordering \u003c/h3\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eThe ordering of the values in an enum type is the order in which the values were listed when the type was created. All standard comparison operators and related aggregate functions are supported for enums. For example:\u003c/p\u003e\n\u003cpre\u003eINSERT INTO person VALUES (\u0026#39;Larry\u0026#39;, \u0026#39;sad\u0026#39;);\nINSERT INTO person VALUES (\u0026#39;Curly\u0026#39;, \u0026#39;ok\u0026#39;);\nSELECT * FROM person WHERE current_mood \u0026gt; \u0026#39;sad\u0026#39;;\n name  | current_mood\n-------+--------------\n Moe   | happy\n Curly | ok\n(2 rows)\n\nSELECT * FROM person WHERE current_mood \u0026gt; \u0026#39;sad\u0026#39; ORDER BY current_mood;\n name  | current_mood\n-------+--------------\n Curly | ok\n Moe   | happy\n(2 rows)\n\nSELECT name\nFROM person\nWHERE current_mood = (SELECT MIN(current_mood) FROM person);\n name\n-------\n Larry\n(1 row)\n\u003c/pre\u003e\n\u003c/div\u003e\n\u003cdiv id=\"DATATYPE-ENUM-TYPE-SAFETY\"\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003ch3\u003e8.7.3. Type Safety \u003c/h3\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eEach enumerated data type is separate and cannot be compared with other enumerated types. See this example:\u003c/p\u003e\n\u003cpre\u003eCREATE TYPE happiness AS ENUM (\u0026#39;happy\u0026#39;, \u0026#39;very happy\u0026#39;, \u0026#39;ecstatic\u0026#39;);\nCREATE TABLE holidays (\n    num_weeks integer,\n    happiness happiness\n);\nINSERT INTO holidays(num_weeks,happiness) VALUES (4, \u0026#39;happy\u0026#39;);\nINSERT INTO holidays(num_weeks,happiness) VALUES (6, \u0026#39;very happy\u0026#39;);\nINSERT INTO holidays(num_weeks,happiness) VALUES (8, \u0026#39;ecstatic\u0026#39;);\nINSERT INTO holidays(num_weeks,happiness) VALUES (2, \u0026#39;sad\u0026#39;);\nERROR:  invalid input value for enum happiness: \u0026#34;sad\u0026#34;\nSELECT person.name, holidays.num_weeks FROM person, holidays\n  WHERE person.current_mood = holidays.happiness;\nERROR:  operator does not exist: mood = happiness\n\u003c/pre\u003e\n\u003cp\u003eIf you really need to do something like that, you can either write a custom operator or add explicit casts to your query:\u003c/p\u003e\n\u003cpre\u003eSELECT person.name, holidays.num_weeks FROM person, holidays\n  WHERE person.current_mood::text = holidays.happiness::text;\n name | num_weeks\n------+-----------\n Moe  |         4\n(1 row)\n\n\u003c/pre\u003e\n\u003c/div\u003e\n\u003cdiv id=\"DATATYPE-ENUM-IMPLEMENTATION-DETAILS\"\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003ch3\u003e8.7.4. Implementation Details \u003c/h3\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eEnum labels are case sensitive, so \u003ccode\u003e\u0026#39;happy\u0026#39;\u003c/code\u003e is not the same as \u003ccode\u003e\u0026#39;HAPPY\u0026#39;\u003c/code\u003e. White space in the labels is significant too.\u003c/p\u003e\n\u003cp\u003eAlthough enum types are primarily intended for static sets of values, there is support for adding new values to an existing enum type, and for renaming values (see \u003ca href=\"/docs/18/sql-altertype.html\" title=\"ALTER TYPE\" rel=\"nofollow\"\u003e\u003cspan\u003eALTER TYPE\u003c/span\u003e\u003c/a\u003e). Existing values cannot be removed from an enum type, nor can the sort ordering of such values be changed, short of dropping and re-creating the enum type.\u003c/p\u003e\n\u003cp\u003eAn enum value occupies four bytes on disk. The length of an enum value\u0026#39;s textual label is limited by the \u003ccode\u003eNAMEDATALEN\u003c/code\u003e setting compiled into \u003cspan\u003ePostgreSQL\u003c/span\u003e; in standard builds this means at most 63 bytes.\u003c/p\u003e\n\u003cp\u003eThe translations from internal enum values to textual labels are kept in the system catalog \u003ca href=\"/docs/18/catalog-pg-enum.html\" rel=\"nofollow\"\u003e\u003ccode\u003epg_enum\u003c/code\u003e\u003c/a\u003e. Querying this catalog directly can be useful.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/div\u003e","SourceRevision":"555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f","ContentHash":"783cc027a7526cea6c85eb1d657d0031de95b718866582b82c00d7fa10559f21","Payload":{"description":["Enumerated (enum) types are data types that comprise a static, ordered set of values. They are equivalent to the enum types supported in a number of programming languages. An example of an enum type might be the days of the week, or a set of status values for a piece of data."],"manual_html":"\u003cdiv class=\"sect1\" id=\"DATATYPE-ENUM\"\u003e\n\u003cdiv class=\"titlepage\"\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003ch2 class=\"title\"\u003e8.7. Enumerated Types \u003c/h2\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\n\u003cp\u003eEnumerated (enum) types are data types that comprise a static, ordered set of values. They are equivalent to the \u003ccode class=\"type\"\u003eenum\u003c/code\u003e types supported in a number of programming languages. An example of an enum type might be the days of the week, or a set of status values for a piece of data.\u003c/p\u003e\n\u003cdiv class=\"sect2\" id=\"DATATYPE-ENUM-DECLARATION\"\u003e\n\u003cdiv class=\"titlepage\"\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003ch3 class=\"title\"\u003e8.7.1. Declaration of Enumerated Types \u003c/h3\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eEnum types are created using the \u003ca class=\"xref\" href=\"/docs/18/sql-createtype.html\" title=\"CREATE TYPE\"\u003e\u003cspan class=\"refentrytitle\"\u003eCREATE TYPE\u003c/span\u003e\u003c/a\u003e command, for example:\u003c/p\u003e\n\u003cpre class=\"programlisting\"\u003eCREATE TYPE mood AS ENUM ('sad', 'ok', 'happy');\n\u003c/pre\u003e\n\u003cp\u003eOnce created, the enum type can be used in table and function definitions much like any other type:\u003c/p\u003e\n\u003cpre class=\"programlisting\"\u003eCREATE TYPE mood AS ENUM ('sad', 'ok', 'happy');\nCREATE TABLE person (\n    name text,\n    current_mood mood\n);\nINSERT INTO person VALUES ('Moe', 'happy');\nSELECT * FROM person WHERE current_mood = 'happy';\n name | current_mood\n------+--------------\n Moe  | happy\n(1 row)\n\u003c/pre\u003e\n\u003c/div\u003e\n\u003cdiv class=\"sect2\" id=\"DATATYPE-ENUM-ORDERING\"\u003e\n\u003cdiv class=\"titlepage\"\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003ch3 class=\"title\"\u003e8.7.2. Ordering \u003c/h3\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eThe ordering of the values in an enum type is the order in which the values were listed when the type was created. All standard comparison operators and related aggregate functions are supported for enums. For example:\u003c/p\u003e\n\u003cpre class=\"programlisting\"\u003eINSERT INTO person VALUES ('Larry', 'sad');\nINSERT INTO person VALUES ('Curly', 'ok');\nSELECT * FROM person WHERE current_mood \u0026gt; 'sad';\n name  | current_mood\n-------+--------------\n Moe   | happy\n Curly | ok\n(2 rows)\n\nSELECT * FROM person WHERE current_mood \u0026gt; 'sad' ORDER BY current_mood;\n name  | current_mood\n-------+--------------\n Curly | ok\n Moe   | happy\n(2 rows)\n\nSELECT name\nFROM person\nWHERE current_mood = (SELECT MIN(current_mood) FROM person);\n name\n-------\n Larry\n(1 row)\n\u003c/pre\u003e\n\u003c/div\u003e\n\u003cdiv class=\"sect2\" id=\"DATATYPE-ENUM-TYPE-SAFETY\"\u003e\n\u003cdiv class=\"titlepage\"\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003ch3 class=\"title\"\u003e8.7.3. Type Safety \u003c/h3\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eEach enumerated data type is separate and cannot be compared with other enumerated types. See this example:\u003c/p\u003e\n\u003cpre class=\"programlisting\"\u003eCREATE TYPE happiness AS ENUM ('happy', 'very happy', 'ecstatic');\nCREATE TABLE holidays (\n    num_weeks integer,\n    happiness happiness\n);\nINSERT INTO holidays(num_weeks,happiness) VALUES (4, 'happy');\nINSERT INTO holidays(num_weeks,happiness) VALUES (6, 'very happy');\nINSERT INTO holidays(num_weeks,happiness) VALUES (8, 'ecstatic');\nINSERT INTO holidays(num_weeks,happiness) VALUES (2, 'sad');\nERROR:  invalid input value for enum happiness: \"sad\"\nSELECT person.name, holidays.num_weeks FROM person, holidays\n  WHERE person.current_mood = holidays.happiness;\nERROR:  operator does not exist: mood = happiness\n\u003c/pre\u003e\n\u003cp\u003eIf you really need to do something like that, you can either write a custom operator or add explicit casts to your query:\u003c/p\u003e\n\u003cpre class=\"programlisting\"\u003eSELECT person.name, holidays.num_weeks FROM person, holidays\n  WHERE person.current_mood::text = holidays.happiness::text;\n name | num_weeks\n------+-----------\n Moe  |         4\n(1 row)\n\n\u003c/pre\u003e\n\u003c/div\u003e\n\u003cdiv class=\"sect2\" id=\"DATATYPE-ENUM-IMPLEMENTATION-DETAILS\"\u003e\n\u003cdiv class=\"titlepage\"\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\n\u003ch3 class=\"title\"\u003e8.7.4. Implementation Details \u003c/h3\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eEnum labels are case sensitive, so \u003ccode class=\"type\"\u003e'happy'\u003c/code\u003e is not the same as \u003ccode class=\"type\"\u003e'HAPPY'\u003c/code\u003e. White space in the labels is significant too.\u003c/p\u003e\n\u003cp\u003eAlthough enum types are primarily intended for static sets of values, there is support for adding new values to an existing enum type, and for renaming values (see \u003ca class=\"xref\" href=\"/docs/18/sql-altertype.html\" title=\"ALTER TYPE\"\u003e\u003cspan class=\"refentrytitle\"\u003eALTER TYPE\u003c/span\u003e\u003c/a\u003e). Existing values cannot be removed from an enum type, nor can the sort ordering of such values be changed, short of dropping and re-creating the enum type.\u003c/p\u003e\n\u003cp\u003eAn enum value occupies four bytes on disk. The length of an enum value's textual label is limited by the \u003ccode class=\"symbol\"\u003eNAMEDATALEN\u003c/code\u003e setting compiled into \u003cspan class=\"productname\"\u003ePostgreSQL\u003c/span\u003e; in standard builds this means at most 63 bytes.\u003c/p\u003e\n\u003cp\u003eThe translations from internal enum values to textual labels are kept in the system catalog \u003ca class=\"link\" href=\"/docs/18/catalog-pg-enum.html\" title=\"52.20. pg_enum\"\u003e\u003ccode class=\"structname\"\u003epg_enum\u003c/code\u003e\u003c/a\u003e. Querying this catalog directly can be useful.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/div\u003e","related":[],"sections":[]}},"RequestedLocale":"zh-Hans","Fallback":true,"Versions":["10","11","12","13","14","15","16","17","18","19","20"],"Locales":["en"],"Signatures":null,"Spellings":null,"SQLState":null,"Evidence":null}