> For the complete documentation index, see [llms.txt](https://docs.postgresql.tw/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.postgresql.tw/internals/catalogs/catalog-pg-enum.md).
# 52.20. pg\_enum \#
The `pg_enum` catalog contains entries showing the values and labels for each enum type. The internal representation of a given enum value is actually the OID of its associated row in `pg_enum`.
**Table 52.20. `pg_enum` Columns**
| Column Type
Description
|
| -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| oid oid
Row identifier
|
| enumtypid oid (references pg\_type.oid)
The OID of the pg\_type entry owning this enum value
|
| enumsortorder float4
The sort position of this enum value within its enum type
|
| enumlabel name
The textual label for this enum value
|
The OIDs for `pg_enum` rows follow a special rule: even-numbered OIDs are guaranteed to be ordered in the same way as the sort ordering of their enum type. That is, if two even OIDs belong to the same enum type, the smaller OID must have the smaller `enumsortorder` value. Odd-numbered OID values need bear no relationship to the sort order. This rule allows the enum comparison routines to avoid catalog lookups in many common cases. The routines that create and alter enum types attempt to assign even OIDs to enum values whenever possible.
When an enum type is created, its members are assigned sort-order positions 1..*`n`*. But members added later might be given negative or fractional values of `enumsortorder`. The only requirement on these values is that they be correctly ordered and unique within each enum type.
***
原文：[PostgreSQL 18.6 Documentation](https://www.postgresql.org/docs/18/catalog-pg-enum.html)（英文原文，待翻譯）
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