37.18. constraint\_column\_usage

|37.18. `constraint_column_usage`|                             |                                  |                  |                                               |
|:------------------------------:|-----------------------------|----------------------------------|------------------|-----------------------------------------------|
|[Prev](infoschema-columns.html) |[Up](information-schema.html)|Chapter 37. The Information Schema|[Home](index.html)| [Next](infoschema-constraint-table-usage.html)|

---

## 37.18. `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 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.

**Table 37.16. `constraint_column_usage` Columns**

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

---

|[Prev](infoschema-columns.html)|[Up](information-schema.html)| [Next](infoschema-constraint-table-usage.html)|
|:------------------------------|:---------------------------:|----------------------------------------------:|
|       37.17. `columns`        |     [Home](index.html)      |        37.19. `constraint_table_usage`        |

 // \<![CDATA[ \<-- For SVG support if ('WebSocket' in window) { (function() { function refreshCSS() { var sheets = [].slice.call(document.getElementsByTagName("link")); var head = document.getElementsByTagName("head")[0]; for (var i = 0; i \< sheets.length; ++i) { var elem = sheets[i]; head.removeChild(elem); var rel = elem.rel; if (elem.href && typeof rel != "string" || rel.length == 0 || rel.toLowerCase() == "stylesheet") { var url = elem.href.replace(/(&|\\?)\_cacheOverride=\\d+/, ''); elem.href = url + (url.indexOf('?') \>= 0 ? '&' : '?') + '\_cacheOverride=' + (new Date().valueOf()); } head.appendChild(elem); } } var protocol = window.location.protocol === 'http:' ? 'ws://' : 'wss://'; var address = protocol + window.location.host + window.location.pathname + '/ws'; var socket = new WebSocket(address); socket.onmessage = function(msg) { if (msg.data == 'reload') window.location.reload(); else if (msg.data == 'refreshcss') refreshCSS(); }; console.log('Live reload enabled.'); })(); } // ]]\>