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
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. |
Returns
Object - The value from the first row and first column of the results. - Returns None if no rows were returned.
Scope
Gateway
Syntax
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. |
| String | tx | A transaction identifier. If omitted, the query will be executed in its own transaction. |
Returns
Object - The value from the first row and first column of the results. - Returns None if no rows were returned.
Scope
Vision Client
Code Examples
# This code would count the number of active alarms, and acknowledge 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")
# This code would read a single value from a table and show it to the user an a popup box.
level = system.db.runScalarQuery("SELECT Level FROM LakeInfo WHERE LakeId='Tahoe'")
system.gui.messageBox("The lake level is: %d feet" % level)
lakeLevel = system.db.runScalarQuery(query)
system.gui.messageBox("The lake level is: %d feet" % lakeLevel)