Query of Queries user guide

If you know SQL or have interacted with databases, you might be familiar with some of the Query of Queries functionality.

Using dot notation

Query of Queries supports using dot notation in table names.

Example

If a structure named A contains a field named B, which contains a table named Products, you can refer to the table with dot notation, as follows:

SELECT tape_ID, length 
FROM A.B.Products;

Using joins

A join operation uses a single SELECT statement to return a result set from multiple, related tables, typically those tables with a primary key - foreign key relationship. The two SQL clauses that perform joins are:

  • WHERE clause: Query of Queries supports joins through a WHERE clause.

  • INNER JOIN and OUTER JOIN: Query of Queries does not support joins through INNER JOIN or OUTER JOIN clauses.

Note: Query of Queries supports joins between two tables only.

Using unions

The UNION operator lets you combine the results of two or more SELECT expressions into a single recordset. The original tables must have the same number of columns, and corresponding columns must be UNION-compatible data types. Columns are UNION-compatible data types if they meet one of the following conditions:

  • The same data type; for example, both Tinyint

  • Both Numeric; for example, Tinyint, Smallint, Integer, Bigint, Double, Float, Real, Decimal, or Numeric

  • Both Characters; for example, Char, Varchar, or LongVarchar

  • Both Dates; for example, Time, TimeStamp, or Date

Note: Query Of Queries does not support ODBC-formatted dates and times.

Syntax

select_expression = select_expression UNION [ALL] select_expression

Example

This example uses the following tables:

Table1

Type(int)

Name(varchar)

1

Tennis

2

Baseball

3

Football

Table2

ID(int)

Sport(varchar)

3

Football

4

Volleyball

5

PingPong

To combine Table1 and Table2, use a UNION statement, as follows:

SELECT * FROM Table1  
UNION  
SELECT * FROM Table2 

The UNION statement produces the following result (UNION) table:

Result table

Type(int)

Name(varchar)

1

Tennis

2

Baseball

3

Football

4

Volleyball

5

PingPong

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; Query of Queries 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  
)  
UNION  
SELECT * FROM TableC 

In the first statement, there are no duplicates in the union between TableB and TableC. Then, in the union between that set and TableA, the ALL keyword includes the duplicates. In the second statement, duplicates are included in the union between TableA and TableB but are eliminated in the subsequent union with TableC. The ALL keyword has no effect on the final result of this expression.

Using other keywords with UNION

When you perform a UNION, the individual SELECT statements cannot have their own ORDER BY or COMPUTE clauses. You can only have one ORDER BY or COMPUTE clause after the last SELECT statement; this clause is applied to the final, combined result set. You can only specify GROUP BY and HAVING expressions in the individual SELECT statements.

Using conditional operators

Query of Queries lets you use the following conditional operators in your SQL statements:

Test conditional

This conditional tests whether a Boolean expression is True, False, or Unknown.

Syntax

cond_test ::= expression [IS [NOT] {TRUE | FALSE | UNKNOWN} ]

Example

SELECT _isValid FROM Chemicals 
WHERE _isValid IS true;

Null conditional

This conditional tests whether an expression is null.

Syntax

null_cond ::= expression IS [NOT] NULL 

Example

SELECT bloodVal FROM Standards 
WHERE bloodVal IS NOT null;

Comparison conditional

This conditional lets you compare an expression against another expression of the same data type (Numeric, String, Date, or Boolean). You can use it to selectively retrieve only the relevant rows of a recordset.

Syntax

comparison_cond ::= expression [> | >= | <> | != | < | <=] expression 

Example

The following example uses a comparison conditional to retrieve only those dogs whose IQ is at least 150:

SELECT dog_name, dog_IQ 
FROM Dogs 
WHERE dog_IQ >= 150;

BETWEEN conditional

This conditional lets you compare an expression against another expression. You can use it to selectively retrieve only the relevant rows of a recordset. Like the comparison conditional, the BETWEEN conditional also compares; however, the BETWEEN conditional compares against a range of values. Therefore, its syntax requires two values, which are inclusive, a minimum and a maximum. Separate these values with the AND keyword.

Syntax

between_cond ::= expression [NOT] BETWEEN expression AND expression 

Example

The following example uses a BETWEEN conditional to retrieve only those dogs whose IQ is between 150 and 165, inclusive:

SELECT dog_name, dog_IQ 
FROM Dogs 
WHERE dog_IQ BETWEEN 150 AND 165;

IN conditional

This conditional lets you specify a comma-delimited list of conditions to match. It is similar in function to the OR conditional. In addition to being more legible when working with long lists, the IN conditional can contain another SELECT statement.

Syntax

in_cond ::= expression [NOT] IN (expression_list) 

Example

The following example uses the IN conditional to retrieve only those dogs who were born at either Ken’s Kennels or Barb’s Breeders:

SELECT dog_name, dog_IQ, Kennel_ID 
FROM Dogs 
WHERE kennel_ID IN ('Kens','Barbs');

LIKE conditional

This conditional lets you perform wildcard searches, in which you compare your data to search patterns. This strategy differs from other conditionals, such as BETWEEN or IN, because the LIKE conditional compares your data to a value that is partially unknown.

Syntax

like_cond ::= left_string_exp [NOT] LIKE right_string_exp [ESCAPE escape_char] 

The left_string_exp can be either a constant string, or a column reference to a string column. The right_string_exp can be either a column reference to a string column, or a search pattern. A search pattern is a search condition that consists of literal text and at least one wildcard character. A wildcard character is a special character that represents an unknown part of a search pattern, and is interpreted as follows:

  • The underscore (_) represents any single character.

  • The percent sign (%) represents zero or more characters.

  • Brackets [ ] represents any character in the range.

  • Brackets with a caret [^] represent any character not in the range.

  • All other characters represent themselves.

Note: Earlier versions of ColdFusion do not support bracketed ranges.

Examples

The following example uses the LIKE conditional to retrieve only those dogs of the breed Terrier, whether the dog is a Boston Terrier, Jack Russell Terrier, Scottish Terrier, and so on:

SELECT dog_name, dog_IQ, breed 
FROM Dogs 
WHERE breed LIKE '%Terrier';

The following examples are select statements that use bracketed ranges:

SELECT lname FROM Suspects WHERE lname LIKE 'A[^c]%'; 
SELECT lname FROM Suspects WHERE lname LIKE '[a-m]%'; 
SELECT lname FROM Suspects WHERE lname LIKE '%[]'; 
SELECT lname FROM Suspects WHERE lname LIKE 'A[%]%'; 
SELECT lname FROM Suspects WHERE lname LIKE 'A[^c-f]%';

Case sensitivity

Unlike the rest of ColdFusion, Query of Queries is case-sensitive. However, Query of Queries supports two string functions, UPPER() and LOWER(), which you can use to achieve case-insensitive matching.

Examples

The following example matches only 'Sylvester':

SELECT dog_name 
FROM Dogs 
WHERE dog_name LIKE 'Sylvester';

The following example is not case sensitive; it uses the LOWER() function to treat 'Sylvester', 'sylvester', 'SYLVESTER', and so on, as all lowercase, and matches them with the all lowercase string, ‘sylvester’:

SELECT dog_name 
FROM Dogs 
WHERE LOWER(dog_name) LIKE 'sylvester';

If you use a variable on the right side of the LIKE conditional and want to ensure that the comparison is not case-sensitive, use the LCase or UCase function to force the variable text to be all of one case, as in the following example:

WHERE LOWER(dog_name) LIKE '#LCase(FORM.SearchString)#';

Escaping wildcards

You can specify your own escape character by using the conditional ESCAPE clause.

Example

The following example uses the ESCAPE clause to enable a search for a literal percent sign (%), which ColdFusion normally interprets as a wildcard character:

SELECT emp_discount 
FROM Benefits 
WHERE emp_discount LIKE '10\%'  
ESCAPE '\';

Managing data types for columns

A Query of Queries requires that every column has metadata that defines the data type of the column. All queries that ColdFusion creates have metadata. However, a query created with QueryNew function that omits the second parameter does not contain metadata. You use this optional second parameter to define the data type of each column in the query.

Specify column data types in the QueryNew function

 Type a QueryNew function, specifying the column names in the first parameter and the data types in the second parameter, as the following example shows:
<cfset qInstruments = queryNew("name, instrument, years_playing", "CF_SQL_VARCHAR, CF_SQL_VARCHAR, CF_SQL_INTEGER")>
Note: To see the metadata for a Query of Queries, use the GetMetaData function.

Specify the column data types in the QueryAddColumn function

  1. Create a query by specifying the QueryNew function with no parameters.

    <!--- Make a query. ---> 
    <cfset myQuery = QueryNew("")>
  2. Add and populate a column with the QueryAddColumn function, specifying the data type in the third parameter:

    <!--- Create an array. ---> 
    <cfset FastFoodArray = ArrayNew(1)> 
    <cfset FastFoodArray[1] = "French Fries"> 
    <cfset FastFoodArray[2] = "Hot Dogs"> 
    <cfset FastFoodArray[3] = "Fried Clams"> 
    <cfset FastFoodArray[4] = "Thick Shakes"> 
    <!--- Use the array to add a column to the query. ---> 
    <cfset nColumnNumber = QueryAddColumn(myQuery, "FastFood", "CF_SQL_VARCHAR", 
        FastFoodArray)>

If you do not specify the data type, ColdFusion examines the first 50 rows of each column to determine the data type when performing conditional expressions.

In some cases, ColdFusion can guess a data type that is inappropriate for your application. In particular, if you use columns in a WHERE clause or other conditional expression, the data types must be compatible. If they are not compatible, use the CAST function to recast one of the columns to a compatible data type. For more information on casting, see Using the CAST function. For more information on data type compatibility, see Understanding Query of Queries processing.

Note: Specifying the data type in the QueryNew function helps you avoid compatibility issues.

Using the CAST function

In some cases, the data type of a column is not compatible with the processing you want to do. For example, query columns returned by the cfhttp tag are all of type CF_SQL_VARCHAR, even if the contents are numeric. In this case, use the Query of Queries CAST function to convert a column value into an expression of the correct data type.

The syntax for the CAST function is as follows:

CAST ( expression AS castType )

Where castType is one of the following:

  • BINARY

  • BIGINIT

  • BIT

  • DATE

  • DECIMAL

  • DOUBLE

  • INTEGER

  • TIME

  • TIMESTAMP

  • VARCHAR

For example:

<cfhttp url="http://quote.yahoo.com/download/quotes.csv?Symbols=csco,jnpr&format=sc1l1&ext=.csv" 
    method="GET" 
    name="qStockItems" 
    columns="Symbol,Change,LastTradedPrice" 
    textqualifier="""" 
    delimiter="," 
    firstrowasheaders="no"> 
<cfoutput> 
    <cfdump var="#qStockItems#"> 
    <cfdump var="#qStockItems.getColumnNames()#"> 
</cfoutput> 
 
<cfoutput> 
<cfloop index="i" from="1" to="#arrayLen(qStockItems.getColumnNames())#"> 
    #qStockItems.getMetaData().getColumnTypeName(javaCast("int",i))#<br/> 
</cfloop> 
</cfoutput> 
<cftry> 
    <cfquery name="hello" dbtype="query"> 
        SELECT SUM(CAST(qStockItems.LastTradedPrice as INTEGER))  
        AS SUMNOW from qStockItems 
    </cfquery> 
    <cfcatch>Error in Query of Queries</cfcatch> 
</cftry> 
 
<cfoutput> 
    <cfdump var="#hello#"> 
</cfoutput>

Using aggregate functions

Aggregate functions operate on a set of data and return a single value. Use these functions for retrieving summary information from a table, as opposed to retrieving an entire table and then operating on the recordset of the entire table.

Consider using aggregate functions to perform the following operations:

  • To display the average of a column

  • To count the number of rows for a column

  • To find the earliest date in a column

Since not every relational database management system (RDBMS) supports all aggregate functions, refer to the documentation of your database. The following table lists the aggregate functions that Query of Queries supports:

Function

Description

AVG()

Returns the average (mean) for a column.

COUNT()

Returns the number of rows in a column.

MAX()

Returns the largest value of a column.

MIN()

Returns the lowest value of a column.

SUM()

Returns the sum of values of a column.

Syntax

aggregate_func ::= <COUNT>(* | column_name) | AVG | SUM | MIN | MAX) 
([ALL | DISTINCT] numeric_exp)

Example

The following example uses the AVG() function to retrieve the average IQ of all terriers:

SELECT dog_name, AVG(dog_IQ) AS avg_IQ 
FROM Dogs 
WHERE breed LIKE '%Terrier';

Arbitrary expressions in aggregate functions

Query of Queries supports aggregate functions of any arbitrary expression, as follows:

SELECT lorange, count(lorange+hirange)  
FROM roysched 
GROUP BY lorange;

Aggregate functions in arbitrary expressions

Query of Queries supports mathematical expressions that include aggregate functions, as follows:

SELECT MIN(lorange) + MAX(hirange) 
FROM roysched 
GROUP BY lorange;

Using group by and having expressions

Query of Queries supports the use of any arbitrary arithmetic expression, as long as it is referenced by an alias.

Examples

The following code is correct:

SELECT (lorange + hirange)/2 AS midrange, 
COUNT(*) 
FROM roysched 
GROUP BY midrange;

The following code is correct:

SELECT (lorange+hirange)/2 AS x,  
COUNT(*) 
FROM roysched GROUP BY x      
HAVING x > 10000;

The following code is not supported in Query of Queries:

SELECT (lorange + hirange)/2 AS midrange, 
COUNT(*) 
FROM roysched 
GROUP BY (lorange + hirange)/2;

Using ORDER BY clauses

Query of Queries supports the ORDER BY clause to sort. Make sure that it is the last clause in your SELECT statement. You can sort by multiple columns, by relative column position, by nonselected columns. You can specify a descending sort direction with the DESC keyword (by default, most RDBMS sorts are ascending, which makes the ASC keyword unnecessary).

Syntax

order_by_column ::= ( <IDENTIFIER> | <INTEGER_LITERAL> ) [<ASC> | <DESC>]

Example

The following example shows a simple sort using an ORDER BY clause:

SELECT acetylcholine_levels, dopamine_levels 
FROM results 
ORDER BY dopamine_levels

The following example shows a more complex sort; results are first sorted by ascending levels of dopamine, then by descending levels of acetylcholine. The ASC keyword is unnecessary, and is used only for legibility.

SELECT acetylcholine_levels, dopamine_levels 
FROM results 
ORDER BY 2 ASC, 1 DESC

Using aliases

Query of Queries supports the use of database column aliases. An alias is an alternate name for a database field or value. Query of Queries lets you reuse an alias in the same SQL statement.

One way to create an alias is to concatenate (append) two or more columns to generate a value. For example, you can concatenate a first name and a last name to create the value fullname. Because the new value does not exist in a database, you refer to it by its alias. The AS keyword assigns the alias in the SELECT statement.

Examples

Query of Queries supports alias substitutions in the ORDER BY, GROUP BY, and HAVING clauses.

Note: Query of Queries does not support aliases for table names.
SELECT FirstName + ' ' + LastName AS fullname 
from Employee;

The following examples rely on these two master queries:

<cfquery name="employee" datasource="2pubs"> 
    SELECT * FROM employee 
</cfquery> 
 
<cfquery name="roysched" datasource="2pubs"> 
    SELECT * FROM roysched 
</cfquery>

ORDER BY example

<cfquery name="order_by" dbtype="query"> 
    SELECT (job_id || job_lvl)/2 AS job_value 
    FROM employee  
    ORDER BY job_value 
</cfquery>

GROUP BY example

<cfquery name="group_by" dbtype="query"> 
    SELECT lorange || hirange AS x, count(hirange)  
    FROM roysched  
    GROUP BY x     
</cfquery>

HAVING example

<cfquery name="having" dbtype="query"> 
    SELECT (lorange || hirange)/2 AS x,  
    COUNT(*) 
    FROM roysched GROUP BY x  
    HAVING x > 10000 
</cfquery>

Handling null values

Query of Queries uses Boolean logic to handle conditional expressions. Proper handling of NULL values requires the use of ternary logic. The IS [NOT] NULL clause works correctly in Query of Queries. However the following expressions do not work properly when the column breed is NULL:

WHERE (breed > 'A') 
WHERE NOT (breed > 'A') 

The correct behavior should not include NULL breed columns in the result set of either expression. To avoid this limitation, add an explicit rule to the conditionals and rewrite them in the following forms:

WHERE breed IS NOT NULL AND (breed > 'A') 
WHERE breed IS NOT NULL AND not (breed > 'A')

Concatenating strings

Query of Queries support two string concatenation operators: + and ||, as the following examples show:

LASTNAME + ', ' + FIRSTNAME 
LASTNAME || ', ' || FIRSTNAME

Escaping reserved keywords

ColdFusion has a list of reserved keywords, which are typically part of the SQL language and are not normally used for names of columns or tables. To escape a reserved keyword for a column name or table name, enclose it in brackets.

Important: Earlier versions of ColdFusion let you use some reserved keywords without escaping them.

Examples

Query of Queries supports the following SELECT statement examples:

SELECT [from] FROM parts; 
SELECT [group].firstname FROM [group]; 
SELECT [group].[from] FROM [group];

Query of Queries does not support nested escapes, such as in the following example:

SELECT [[from]] FROM T;

The following table lists ColdFusion reserved keywords:

ABSOLUTE

ACTION

ADD

ALL

ALLOCATE

ALTER

AND

ANY

ARE

AS

ASC

ASSERTION

AT

AUTHORIZATION

AVG

BEGIN

BETWEEN

BIT

BIT_LENGTH

BOTH

BY

CASCADE

CASCADED

CASE

CAST

CATALOG

CHAR

CHARACTER

CHARACTER_LENGTH

CHAR_LENGTH

CHECK

CLOSE

COALESCE

COLLATE

COLLATION

COLUMN

COMMIT

CONNECT

CONNECTION

CONSTRAINT

CONSTRAINTS

CONTINUE

CONVERT

CORRESPONDING

COUNT

CREATE

CROSS

CURRENT

CURRENT_DATE

CURRENT_TIME

CURRENT_TIMESTAMP

CURRENT_USER

CURSOR

DATE

DAY

DEALLOCATE

DEC

DECIMAL

DECLARE

DEFAULT

DEFERRABLE

DEFERRED

DELETE

DESC

DESCRIBE

DESCRIPTOR

DIAGNOSTICS

DISCONNECT

DISTINCT

DOMAIN

DOUBLE

DROP

ELSE

END

END-EXEC

ESCAPE

EXCEPT

EXCEPTION

EXEC

EXECUTE

EXISTS

EXTERNAL

EXTRACT

FALSE

FETCH

FIRST

FLOAT

FOR

FOREIGN

FOUND

FROM

FULL

GET

GLOBAL

GO

GOTO

GRANT

GROUP

HAVING

HOUR

IDENTITY

IMMEDIATE

IN

INDICATOR

INITIALLY

INNER

INPUT

INSENSITIVE

INSERT

INT

INTEGER

INTERSECT

INTERVAL

INTO

IS

ISOLATION

JOIN

KEY

LANGUAGE

LAST

LEADING

LEFT

LEVEL

LIKE

LOCAL

LOWER

MATCH

MAX

MIN

MINUTE

MODULE

MONTH

NAMES

NATIONAL

NATURAL

NCHAR

NEXT

NO

NOT

NULL

NULLIF

NUMERIC

OCTET_LENGTH

OF

ON

ONLY

OPEN

OPTION

OR

ORDER

OUTER

OUTPUT

OVERLAPS

PAD

PARTIAL

POSITION

PRECISION

PREPARE

PRESERVE

PRIMARY

PRIOR

PRIVILEGES

PROCEDURE

PUBLIC

READ

REAL

REFERENCES

RELATIVE

RESTRICT

REVOKE

RIGHT

ROLLBACK

ROWS

SCHEMA

SCROLL

SECOND

SECTION

SELECT

SESSION

SESSION_USER

SET

SMALLINT

SOME

SPACE

 

SQL

SQLCODE

SQLERROR

SQLSTATE

SUBSTRING

SUM

SYSTEM_USER

TABLE

TEMPORARY

THEN

TIME

TIMESTAMP

TIMEZONE_HOUR

TIMEZONE_MINUTE

TO

TRAILING

TRANSACTION

TRANSLATE

TRANSLATION

TRIM

TRUE

UNION

UNIQUE

UNKNOWN

UPDATE

UPPER

USAGE

USER

USING

VALUE

VALUES

VARCHAR

VARYING

VIEW

WHEN

WHENEVER

WHERE

WITH

WORK

WRITE

YEAR

ZONE

 

 

 

Using Queries of Queries with dates

If you create a query object with the QueryNew function and populate a column with date constants, ColdFusion stores the dates as a string inside the query object until a Query of Queries is applied to the query object. When ColdFusion applies a Query of Queries to the query object, it converts the string representations into date objects.

Query of Queries supports date constants in SQL and ODBC format, as follows:

  • SQL format: Dates, times, or timestamps in one of the following format:

    • Date string: yyyy-mm-dd, for example, 1955-06-13.

    • Time string: hh:mm:ss[.[nnn]], for example, 14:34:30.75.

    • Timestamp string: yyyy-mm-dd hh:mm:ss[.[nnn]], for example, 1924-01-14 12:00:00.000.

  • ODBC format: Dates, times, or timestamps in one of the following format:

    • Date string: {d 'value'}, for example, {d '2004-07-06'}.

    • Time string: {t 'value'}, for example, {t '13:45:30'}.

    • Timestamp string: {ts 'value'}, for example, {ts '2004-07-06 13:45:30'}.

If you want to convert the date to its original format, use the DateFormat function and apply the "mm/dd/yy" mask.

Understanding Query of Queries performance

Query of Queries performs well on single-table query objects that were accessed directly from a database. This happens because ColdFusion stores meta information for a query object accessed from a database.

When working with a query resulting in a SQL join, Query of Queries performs as follows:

  1. Query of Queries is efficient for simple joins in which only one equality exists between two column references or constants, for example:

    SELECT T1.a, b, c, d FROM T1, T2 WHERE T1.a = T2.a
  2. Query of Queries is less efficient for joins in which the predicate contains multiple expressions, for example:

    SELECT T1.a, b, c, d FROM T1, T2  
    WHERE T1.a = T2.a AND T1.b + T1.c = T2.b + T2.c

Understanding Query of Queries processing

Query of Queries can process the following:

  • Column comparisons

  • Queries passed by reference

  • Complex objects

Comparing columns with different data types

Starting with ColdFusion MX 7, ColdFusion includes enhancements that allow you to compare columns with different data types.

If one of the operands has a known column type (only constants have an unknown column type), Query of Queries tries to coerce the constant with an unknown type to the type of the operand with metadata. The pairs of allowed coercions are as follows:

  • Binary, string

  • Dates, string

  • Numeric, bigdecimal

  • Boolean, numeric

That is, ColdFusion can coerce between binary and string, but not between date and string.

If both operands have known data types, the types must be the same. The only exception is that ColdFusion can coerce among integer, float, and double.

If both operands are constants, ColdFusion tries to coerce the values, first to the most restrictive type, then to the least restrictive type.

  • First to binary then to string.

  • First to date then to string.

  • First to boolean then to numeric.

Passing queries by reference

A Query of Queries is copied by reference from its related query; which means that ColdFusion does not create a query when you create a Query of Queries. It also means that changes to a Query of Queries, such as ordering, modifying, and deleting data, are also applied to the base query object.

If you do not want the original query to change, use the Duplicate function to create a copy and create the Query of Queries using the copied query.

Managing complex objects

You cannot use Query Of Queries on a recordset that contains complex objects, such as arrays and structures.

Note: You can store a recordset in a complex object.