52.6. pg\_attrdef

|      52.6. `pg_attrdef`      |                   |                           |                  |                                  |
|:----------------------------:|-------------------|---------------------------|------------------|----------------------------------|
|[Prev](catalog-pg-amproc.html)|[Up](catalogs.html)|Chapter 52. System Catalogs|[Home](index.html)| [Next](catalog-pg-attribute.html)|

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## 52.6. `pg_attrdef`

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 The catalog `pg_attrdef` stores column default values. The main information about columns is stored in [`pg_attribute`](catalog-pg-attribute.html). Only columns for which a default value has been explicitly set will have an entry here.

**Table 52.6. `pg_attrdef` Columns**

|                                                                  Column Type<br/><br/> Description                                                                 |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|                                                                `oid` `oid`<br/><br/> Row identifier                                                                |
|                         `adrelid` `oid` (references [`pg_class`](catalog-pg-class.html).`oid`)<br/><br/> The table this column belongs to                          |
|                        `adnum` `int2` (references [`pg_attribute`](catalog-pg-attribute.html).`attnum`)<br/><br/> The number of the column                         |
|`adbin` `pg_node_tree`<br/><br/> The column default value, in `nodeToString()` representation. Use `pg_get_expr(adbin, adrelid)` to convert it to an SQL expression.|

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|[Prev](catalog-pg-amproc.html)|[Up](catalogs.html)| [Next](catalog-pg-attribute.html)|
|:-----------------------------|:-----------------:|---------------------------------:|
|      52.5. `pg_amproc`       |[Home](index.html) |       52.7. `pg_attribute`       |

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