July 2002
Beginner
424 pages
9h 30m
English
Content preview from SQL: Visual QuickStart Guide
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Qualifying Column Names
Recall from “Tables, Columns, and Rows” in Chapter 2 that column names must be unique within a table but can be reused in other tables. The tables authors and publishers in the sample database both contain a column named city, for example.
To identify an otherwise-ambiguous column uniquely in a query that involves multiple tables, use its qualified name. A qualified name is a table name followed by a dot and the name of the column in the table. Because tables must have different names within a database, a qualified name uniquely identifies a single column within the entire database.
To qualify a column name:
- Type:
column is a column name, and table is name of the table that contains column (Listing 7.1 ...
table.column
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