SQL Tutorial

Once we have the information in the table, we might find that there is a need to modify the data. To do so, we can use the UPDATE command. The syntax for this is

UPDATE "table_name"
SET "column_1" = [new value]
WHERE {condition}

It is easiest to use an example. Say we currently have a table as below:

Table Store_Information

store_name	Sales	Date
Los Angeles	$1500	Jan-05-1999
San Diego	$250	Jan-07-1999
Los Angeles	$300	Jan-08-1999
Boston	$700	Jan-08-1999

We find that the sales for Los Angeles on 01/08/1999 is actually $500 instead of $300, and we need to update that particular entry. To do so, we use the following SQL:

UPDATE Store_Information
SET Sales = 500
WHERE store_name = "Los Angeles"
AND Date = "Jan-08-1999"

The resulting table would look like

Table Store_Information

store_name	Sales	Date
Los Angeles	$1500	Jan-05-1999
San Diego	$250	Jan-07-1999
Los Angeles	$500	Jan-08-1999
Boston	$700	Jan-08-1999

In this case, there is only one row that satisfies the condition in the WHERE clause. If there are two rows that satisfy the condition, both rows will be modified.

It is also possible to UPDATE multiple columns at the same time. The syntax in this case would look like the following:

UPDATE TABLE "table_name"
SET ("column_1", "column_2") = ([new value 1], [new value 2])
WHERE {condition}