revQueryDatabase
Type
function
Summary
Selects records in a database according to a SQL query.
Syntax
revQueryDatabase(<databaseID>, <SQLQuery> [,{<variablesList> | <arrayName>}])
Description
Use the revQueryDatabase function to select records in a database to work on.
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\" && \
\"id=: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. See revDataFromQuery for binary data examples.
To execute a SQL query that does not return a record set (database cursor)(glossary) (such as INSERT or DELETE), use the revExecuteSQL command 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.
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 pane of the Standalone Application Settings window, make sure both the "Database" library checkbox and those of the database drivers you are using are checked.
Parameters
| Name | Type | Description |
|---|---|---|
databaseID | The number returned by the revOpenDatabase function when the database was opened. | |
SQLQuery | string | A string in Structured Query Language that contains a SELECT statement. (Do not include a semicolon at the end of the SQLQuery.) |
variablesList | 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]". | |
arrayName | array | The name of a single array variable whose keys are sequential numbers.
|
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]")
Related
command: revCloseCursor, revExecuteSQL
control structure: function
function: revDataFromQuery, revQueryIsAtStart
glossary: command, LiveCode custom library, variable, element, standalone application, binary file, array, prepend, SQL query, record set, return value, record, Standalone Application Settings, database
library: Database library
Compatibility and Support
Introduced
LiveCode 1.1
OS
mac
windows
linux
ios
android
Platforms
desktop
server
mobile