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3 where cust_id = 28983;
CUST_ID CUST_CREDIT_LIMIT
---------- -----------------
28983 15000
SQL> update customers
2 set cust_credit_limit = 20000
3 where cust_id = 28983;
1 row updated.
SQL> select cust_id, cust_credit_limit
2 from customers
3 where cust_id = 28983;
CUST_ID CUST_CREDIT_LIMIT
---------- -----------------
28983 20000
This example reveals that customer 28983 had a $15,000 credit limit before the update statement was executed. The update statement is written against the CUSTOMERS table with a set clause issued against the column to be changed, cust_credit_limit, and a where clause to make the change only for customer 28983. After the command is executed, a select statement reveals that the customer now has a credit limit of $20,000. The update statement is a very powerful tool. It can be used against one record, multiple records meeting simple or complex criteria, or all records in a table.
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Ask the Expert |
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Q: Can you use a where clause with every type of DML statement? |
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A: The where clause can be used only with select, update, and delete statements. The insert statement can never have a where clause. |
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Q: You mentioned that a where clause is optional for update statements. What would happen if one isn't used during an update? |
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A: If a where clause isn't used with an update statement, every record in the table will be updated. |
