Using Conditional Retrieval › Combining Predicates

Combining Predicates

You can combine predicates with AND and OR:

• Use AND when all predicates must be true
• Use OR when only one predicate must be true

The default order of evaluation is AND before OR. You can use parentheses to override the default order.

How It's Done

The Human Resources department needs to identify employees who live in Camden, Brookline, or Canton and who have telephones in order to set up a calling network. You created both of these search conditions earlier in this chapter. Now you want to combine them.

To produce this list, enter:

select emp_id, city, phone
       from employee
       where city in ('Camden', 'Brookline', 'Canton')
        and phone is not null;

The result looks like this:

EMP_ID  CITY                  PHONE
------  ----                  -----
  3338  Canton                6179238844
  3082  Camden                5089273644
  4660  Camden                5092344620
  2209  Brookline             6175563331
  5090  Canton                5083389935
  3222  Brookline             6176635520
  2096  Brookline             6175553643
  5103  Brookline             6176600684
  5008  Brookline             6176642209
  3764  Brookline             6179458377
  1234  Brookline             6176646602
  2174  Brookline             6176633854
  4703  Brookline             6176648290
  3294  Brookline             6175567551
  3118  Canton                5083766984

15 rows processed