Expressions are used to calculate data values. An expression is a combination of one or more components, such as numeric values, operators, and SQL functions. In general, an expression assumes the data types of its components.
The values of the
NLS_SORT parameters jointly affect the sorting and comparison of characters. If the
NLS_COMP parameter in the database is set to
LINGUISTIC, all the entities described in this chapter follow the rules that are specified by the
NLS_SORT parameter. If the
NLS_COMP parameter is not set to
LINGUISTIC, the functions are not affected by
NLS_SORT. You can directly specify the value of
NLS_SORT. If you do not specify it, it inherits the value of
The result of the following simple expression is 4 and of the
NUMBER data type. This data type is consistent with the data type of the components.
The following complex expression uses functions and operators. This expression adds seven days to the current date, removes the time portion, and then converts the result to the
CHAR data type.
You can also use expressions in the following scenarios:
- The selected columns in
START WITH, and
For example, you can use an expression to replace the string Smith in the
SET clause of the following
SET last_name = 'Smith';
SET clause, the expression
INITCAP(last_name) is used to replace the string Smith.
SET last_name = INITCAP(last_name);
In ApsaraDB for OceanBase, not all expressions can be directly used by SQL statements. For more information, see the limits on expressions in the SQL statements topic.