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error 404 revQueryDatabase | revDocs | RunRev
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Product Edition
Version
revQueryDatabase
Basics
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Type
Function
Syntax

revQueryDatabase(databaseID,SQLQuery[,{variablesList | arrayName}])

Introduced
1.1
Changed
2.0
Environment
Desktop, Web and Server
Platform Support
MacOS,Mac OS X,Windows,Linux
Security
Disk,Network
Summary
Selects records in a database according to a SQL query.
Examples

revQueryDatabase(2,"SELECT * FROM EmpStats")
revQueryDatabase(currentDB,field "Query")
revQueryDatabase(the database of me,myQuery,"myVar1","myVar2","myVar3")
revQueryDatabase(tConnectionId, tQuery, "tInputData[id]", "tInputData[name]")

Additional Comments
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Use the revQueryDatabase function to select records in a database to work on.

Parameters:

The databaseID is the number returned by the revOpenDatabase function when the database was opened.

The SQLQuery is a string in Structured Query Language that contains a SELECT statement. (Do not include a semicolon at the end of the SQLQuery.)

The variablesList consists of one or more variable names (or expressions that evaluate to variable names), separated by commas. As of version 2.9, each variable name can also be the name of an array element, for example "tInputData[myKey]".

The arrayName is the name of a single array variable whose keys are sequential numbers.

Note: The variable names or arrayName must be enclosed in quotes; otherwise, the variable's value rather than its name is passed to the revQueryDatabase function.

Value:

The revQueryDatabase function returns a record set ID which designates the record set (database cursor) selected by the SQLQuery. The record set ID is an integer.

Comments:

The SQLQuery may contain one or more placeholders, which are sequential numbers prepended by a colon. The revQueryDatabase function substitutes the corresponding variable name in the variablesList for each of these placeholders. For example, if you have two variables called "valueX" and "valueY", you can use a SQLQuery that includes placeholders as follows:

get revQueryDatabase(myID,"SELECT * FROM empStats WHERE id=:1 OR stat_id=:1 OR population=:2","valueX","valueY")

The content of the variable valueX is substituted for the ":1" in the SQLQuery (in both places where ":1" appears), and the content of valueY is substituted for ":2".

If you specify an arrayName rather than a list of ordinary variables, the revQueryDatabase function substitutes the corresponding element of the array for each of the placeholders in the query:

get revQueryDatabase(myID,"SELECT :1,:2 FROM empStats WHERE 1",myArray)

The content of the element myArray[1] is substituted for the ":1" in the SQLQuery (in both places where ":1" appears), and the content of myArray[2] is substituted for ":2".

To pass binary data in a variable in the variablesList, prepend "*b" to the variable name. The revQueryDatabase function strips the binary marker "*b" and passes it to the database as binary data, rather than text data. To pass binary data in an array element, prepend "*b" to the element's value.

Tip: To execute a SQL query that does not return a record set (database cursor) (such as INSERT or DELETE), use the revExecuteSQLcommand instead. Since revExecuteSQL does not allocate storage for returned data, it is more efficient than revQueryDatabase for SQL queries where no data is returned.

If the query is not successful, the revQueryDatabase function returns an error message. The error message is never an integer, so you can check whether the query was successful by checking whether the return value is an integer or not.

Important! The revQueryDatabase function is part of the Database library. To ensure that the function works in a standalone application, you must include this custom library when you create your standalone. In the Inclusions section of the General screen of the Standalone Application Settings window, make sure the "Database Support" checkbox is checked and the database drivers you are using are selected in the list of database drivers.

Changes to Revolution:

The revQueryDatabase synonym was added in version 2.0.

User Comments
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