Column names
The meaning of a column name depends on its context. A column name can
be used to:
- Declare the name of a column, as in a CREATE TABLE statement.
- Identify a column, as in a CREATE INDEX statement.
- Specify values of the column, as in the following contexts:
- In a aggregate function a column name
specifies all values of the column in the group or intermediate result table
to which the function is applied. Groups and intermediate result tables are
explained under Queries. For example, MAX(SALARY) applies the
function MAX to all values of the column SALARY in a group.
- In a GROUP BY or ORDER BY clause, a column name
specifies all values in the intermediate result table to which the clause
is applied. For example, ORDER BY DEPT orders an intermediate result table
by the values of the column DEPT.
- In an expression, a search
condition, or a scalar function, a column name
specifies a value for each row or group to which the construct is applied.
For example, when the search condition CODE = 20 is applied to some row, the
value specified by the column name CODE is the value of the column CODE in
that row.
- Provide a column name for an expression to temporarily rename
a column, as in the correlation-clause of a table-reference in
a FROM clause, or in the AS clause in the select-clause.
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