SQL - Update Warning!

Be careful when updating records. If we omit the WHERE clause, ALL records will be updated:

Example

UPDATE Customers
SET ContactName='Juan';

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SQL - UPDATE Multiple Records

In an update statement, it is the WHERE clause that determines how many records which will be updated.

The WHERE clause: WHERE Country='Mexico' will update all records which have the value "Mexico" in the field "Country".

Example

UPDATE Customers
SET ContactName='Juan'
WHERE Country='Mexico';

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SQL - UPDATE Multiple Columns

To update more than one column, use a comma as seperator.

Assume we wish to update the customer "Alfreds Futterkiste" with a new contact person and city.

We use the following SQL statement:

Example

UPDATE Customers
SET ContactName='Alfred Schmidt', City='Frankfurt'
WHERE CustomerID=1;

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SQL - ORDER BY Several Columns Example 2

The following SQL statement selects all customers from the "Customers" table, sorted ascending by the "Country" and descending by the "CustomerName" column:

Example

SELECT * FROM Customers
ORDER BY Country ASC, CustomerName DESC;

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SQL - ORDER BY Several Columns Example

The following SQL statement selects all customers from the "Customers" table, sorted by the "Country" and the "CustomerName" column:

Example

SELECT * FROM Customers
ORDER BY Country, CustomerName;

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SQL - ORDER BY DESC Example

The following SQL statement selects all customers from the "Customers" table, sorted DESCENDING by the "Country" column:

Example

SELECT * FROM Customers
ORDER BY Country DESC;

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