30 FileMaker ODBC and JDBC Guide
HAVING clause
The HAVING clause enables you to specify conditions for groups of records (for example, display only the
departments that have salaries totaling more than $200,000). This clause is valid only if you have already
defined a GROUP BY clause. It has the following format:
HAVING expr1 rel_operator expr2
expr1 and expr2 can be field names, constant values, or expressions. These expressions do not have to
match a column expression in the SELECT clause.
rel_operator is the relational operator that links the two expressions. The following example returns only
the departments whose sums of salaries are greater than $200,000:
SELECT dept_id, SUM (salary) FROM emp
GROUP BY dept_id HAVING SUM (salary) > 200000
UNION operator
The UNION operator combines the results of two or more SELECT statements into a single result. The
single result is all of the returned records from the SELECT statements. By default, duplicate records are
not returned. To return duplicate records, use the ALL keyword (UNION ALL). The format is:
SELECT statement UNION [ALL] SELECT statement
When using the UNION operator, the select lists for each SELECT statement must have the same number
of column expressions, with the same data types, and must be specified in the same order. For example:
SELECT last_name, salary, hire_date FROM emp UNION SELECT name, pay,
birth_date FROM person
This example has the same number of column expressions, and each column expression, in order, has the
same data type.
The following example is not valid because the data types of the column expressions are different (SALARY
from EMP has a different data type than LAST_NAME from RAISES). This example has the same number
of column expressions in each SELECT statement, but the expressions are not in the same order by data type.
SELECT last_name, salary FROM emp UNION SELECT salary, last_name FROM raises
ORDER BY clause
The ORDER BY clause indicates how the records are to be sorted. The format is:
ORDER BY {sort_expression [DESC | ASC]}, ...
sort_expression can be field names, expressions, or the positional number of the column expression to
use. The default is to perform an ascending (ASC) sort.
For example, to sort by last_name then by first_name, you could use either of the following SELECT
statements:
SELECT emp_id, last_name, first_name FROM emp ORDER BY last_name, first_name
or
SELECT emp_id, last_name, first_name FROM emp ORDER BY 2,3
In the second example, last_name is the second column expression following SELECT, so ORDER BY 2
sorts by
last_name.
