
464
Chapter 22: Using Query of Queries
The UNION statement produces the following result (UNION) table:
Using aliases for column names
The column names of a UNION table are the column names in the result set of the first SELECT
statement in the UNION operation; ColdFusion ignores the column names in the other
SELECT statement. To change the column names of the result table, you can use an alias, as
follows:
Select Type
as SportType
, Name
as SportName
from Table1
UNION
Select * from Table2
Duplicate rows and multiple tables
By default, the UNION operator removes duplicate rows from the result table. If you use the
keyword ALL, then duplicates are included.
You can combine an unlimited number of tables using the UNION operator, for example:
Select * from Table1
UNION
Select * from Table2
UNION
Select * from Table3
...
Parentheses and evaluation order
By default, the Query of Queries SQL engine evaluates a statement containing UNION operators
from left to right. You can use parentheses to change the order of evaluation. For example, the
following two statements are different:
/* First statement. */
SELECT * FROM TableA
UNION ALL
(SELECT * FROM TableB
UNION
SELECT * FROM TableC
)
/* Second statement. */
(SELECT * FROM TableA
UNION ALL
SELECT * FROM TableB
)
Result table
Type(int)
Name(varchar)
1
Tennis
2 Baseball
3
Football
4
Volleyball
5
PingPong
Содержание COLDFUSION MX 61-DEVELOPING COLDFUSION MX
Страница 1: ...Developing ColdFusion MX Applications...
Страница 22: ...22 Contents...
Страница 38: ......
Страница 52: ...52 Chapter 2 Elements of CFML...
Страница 162: ......
Страница 218: ...218 Chapter 10 Writing and Calling User Defined Functions...
Страница 250: ...250 Chapter 11 Building and Using ColdFusion Components...
Страница 264: ...264 Chapter 12 Building Custom CFXAPI Tags...
Страница 266: ......
Страница 314: ...314 Chapter 14 Handling Errors...
Страница 344: ...344 Chapter 15 Using Persistent Data and Locking...
Страница 349: ...About user security 349...
Страница 357: ...Security scenarios 357...
Страница 370: ...370 Chapter 16 Securing Applications...
Страница 388: ...388 Chapter 17 Developing Globalized Applications...
Страница 408: ...408 Chapter 18 Debugging and Troubleshooting Applications...
Страница 410: ......
Страница 426: ...426 Chapter 19 Introduction to Databases and SQL...
Страница 476: ...476 Chapter 22 Using Query of Queries...
Страница 534: ...534 Chapter 24 Building a Search Interface...
Страница 556: ...556 Chapter 25 Using Verity Search Expressions...
Страница 558: ......
Страница 582: ...582 Chapter 26 Retrieving and Formatting Data...
Страница 668: ......
Страница 734: ...734 Chapter 32 Using Web Services...
Страница 760: ...760 Chapter 33 Integrating J2EE and Java Elements in CFML Applications...
Страница 786: ...786 Chapter 34 Integrating COM and CORBA Objects in CFML Applications...
Страница 788: ......
Страница 806: ...806 Chapter 35 Sending and Receiving E Mail...