# UPDATE Statement

# UPDATE Statement

Existing data in a database can be updated. You can update one row, all rows, or specified rows of data, or update data in a single column without affecting the data in the other columns. The UPDATE statement changes the values of the specified columns in all rows that satisfy the condition. The **WHERE** clause clarifies conditions. The columns to be modified need to be mentioned in the **SET** clause; columns not explicitly modified retain their previous values.

## **Syntax**

```plaintext
""UPDATE table_name 
SET column_name = { expression | DEFAULT } 
[WHERE condition ];
```

## **Parameter Description**

* **table\_name**
    
    Specifies the name (optionally schema-qualified) of the table to be updated. For example, **myshcema.table**.
    
    Value range: an existing table name
    
* **expression**
    
    Specifies the expression or value to be assigned to a column.
    
* **column\_name**
    
    Specifies the name of the column to be modified.
    
    Value range: an existing column name
    
* **condition**
    
    Specifies an expression that returns a value of Boolean type. Only rows for which this expression returns **true** are updated.
    

## **Examples**

Run the following command to change the value of **c\_customer\_sk** in the **customer\_t1** table from **9527** to **9876**:

```plaintext
""openGauss=# UPDATE customer_t1 SET c_customer_sk = 9876 WHERE c_customer_sk = 9527;
UPDATE 1
```

You can use a schema to modify the table name. If no such modifier is specified, the table is located based on the default schema path. In the statement, **SET** is followed by the target column and the new column value. The new column value can be a constant or an expression.

For example, run the following statement to increase all the values in the **c\_customer\_sk** column by 100:

```plaintext
""openGauss=# UPDATE customer_t1 SET c_customer_sk = c_customer_sk + 100;
UPDATE 9
```

This statement does not include the **WHERE** clause, so all rows are updated. If the statement includes the **WHERE** clause, only the rows matching the clause are updated.

In the **SET** clause, the equal sign (=) indicates value setting. In the **WHERE** clause, the equal sign indicates comparison. **WHERE** may not represent an equation and can be replaced by other operators.

You can run an UPDATE statement to update multiple columns by specifying multiple values in the **SET** clause. For example:

```plaintext
""openGauss=# UPDATE customer_t1 SET c_customer_id = 'Admin', c_first_name = 'Local' WHERE c_customer_sk = 4421; 
UPDATE 1
```