---
title: "`constraint_column_usage`"
id: infoschema-constraint-column-usage
pg_version: "20devel"
---

<a id="infoschema-constraint-column-usage"></a>

## 35.18. `constraint_column_usage`

The view `constraint_column_usage` identifies all columns in the current database that are used by some constraint. Only those columns are shown that are contained in a table owned by a currently enabled role. For a check constraint, this view identifies the columns that are used in the check expression. For a not-null constraint, this view identifies the column that the constraint is defined on. For a foreign key constraint, this view identifies the columns that the foreign key references. For a unique or primary key constraint, this view identifies the constrained columns. 

**constraint_column_usage Columns**

| Column Type | Description | 
| --- | --- |
| `table_catalog` `sql_identifier` | Name of the database that contains the table that contains the column that is used by some constraint (always the current database) |
| `table_schema` `sql_identifier` | Name of the schema that contains the table that contains the column that is used by some constraint |
| `table_name` `sql_identifier` | Name of the table that contains the column that is used by some constraint |
| `column_name` `sql_identifier` | Name of the column that is used by some constraint |
| `constraint_catalog` `sql_identifier` | Name of the database that contains the constraint (always the current database) |
| `constraint_schema` `sql_identifier` | Name of the schema that contains the constraint |
| `constraint_name` `sql_identifier` | Name of the constraint |