Appendix B. Expressions, Operators, and Conditions
SQL (Structured Query Language), which we describe in Chapter 7, is the common language used to access the Oracle database. You frequently use some type of logic to specify the data affected by a SQL statement. To implement this logic, you need expressions, operators, and conditions:
- Expressions
Used to define values, for example:
2+2 SYSDATE TO_CHAR(SYSDATE)
- Operators
Used to compare two values, for example:
a = b a != b a AND b
- Conditions
Used to specify acceptable values, for example:
a > b a EXISTS a IS NOT NULL
Expressions, operators, and conditions may be included in a variety of SQL statements, as well as in PL/SQL code. This appendix summarizes the various options available for specifying expressions, operators, and conditions. For a more detailed description of where they can be specified, see Chapter 7 for SQL and Chapter 9 for PL/SQL.
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