system.db.runScalarQuery

This function is used in Python Scripting.

Description

Runs a query against a database connection just like the runQuery function, but only returns the value from the first row and column. If no results are returned from the query, the special value None is returned.

Client Permission Restrictions

Permission Type: Legacy Database Access

Client access to this scripting function is blocked to users that do not meet the role/zone requirements for the above permission type. This function is unaffected when run in the Gateway scope.

Syntax - Gateway

system.db.runScalarQuery(query, database, [tx])

Parameters

Type	Parameter	Description
String	query	A SQL query that should be designed to return one row and one column.
String	database	The name of the database connection to execute against.
String	tx	A transaction identifier. If omitted, the query will be executed in its own transaction. [optional]

Returns

Object - The value from the first row and first column of the results. - Returns None if no rows were returned.

Scope

Gateway

Syntax - Vision and Perspective

system.db.runScalarQuery(query, [database], [tx])

Parameters

Type	Parameter	Description
String	query	A SQL query that should be designed to return one row and one column.
String	database	The name of the database connection to execute against. If omitted or "", the project's default database connection will be used. [optional]
String	tx	A transaction identifier. If omitted, the query will be executed in its own transaction. [optional]

Returns

Any - The value from the first row and first column of the results. Returns None if no rows were returned.

Scope

Vision Client, Perspective Session

Code Examples

Code Snippet

# This code counts the number of active alarms and acknowledges them all if there is at least one.
numAlarms = system.db.runScalarQuery("SELECT COUNT(*) FROM alarmstatus " + "WHERE unacknowledged = 1")
if numAlarms > 0:
   # There are alarms - acknowledge all of them
   system.db.runUpdateQuery("UPDATE alarmstatus SET unacknowledged = 0")

Code Snippet

# This code reads a single value from a table and shows it to the user in a popup.
level = system.db.runScalarQuery("SELECT Level FROM LakeInfo WHERE LakeId='Tahoe'")
system.gui.messageBox("The lake level is: %d feet" % level)