In addition to restricting the number of columns in a base table, it is also possible to restrict the number of rows. Rows are selected by formulating a WHERE condition.
Selection of rows with the city 'New York':
SELECT title, firstname, name, city
FROM customer
WHERE city = 'New York'
Selection of rows with an account of 0.00:
SELECT name, city, account
FROM customer
WHERE account = 0.00
Now those rows are to be selected which have no value in a specified column.
"no value" is not indicated by the value "0" or " ", but by NULL.
SELECT title, firstname, name
FROM customer
WHERE firstname IS NULL
SELECT name, city
FROM customer
WHERE account IS NULL
***ERROR 100 ROW NOT FOUND
If only the first five columns are to be output, and provided with numbers, the statement is as follows:
SELECT ROWNO, cno, title, firstname, name
FROM customer
WHERE ROWNO <= 5
Then the result is:
