# Handle Named Query Timeout in Python

**URL:** <https://forum.inductiveautomation.com/t/handle-named-query-timeout-in-python/66397>\
**Category:** Ignition\
**Tags:** ignition81, vision, scripting\
**Created:** [November 11, 2022, 3:39pm UTC](https://forum.inductiveautomation.com/t/handle-named-query-timeout-in-python/66397 "2022-11-11T15:39:08Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![amarks](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/amarks/32/45610_2.png) [@amarks](https://forum.inductiveautomation.com/u/amarks)\
**Post date:** [November 11, 2022, 3:39pm UTC](https://forum.inductiveautomation.com/t/handle-named-query-timeout-in-python/66397/1 "2022-11-11T15:39:08Z")

</div>

I have a script for comparing the current value of a tag to the last value stored in the DB for that tag, and then storing the current value. Of course, this means I have to run a query to read the last value. The call looks like this:

```auto
lastDBvalue = system.db.runNamedQuery("Project", "Read_DB", {"tag_name" : PlcTag})

```

This query works, and calling it works, but how do I handle the situation where this is the first entry in the table for the tag? When the query times out, what is the value of `lastDBvalue`?

Currently, this is how I have it written, but it doesn't seem to be working for the last 3 tags that I added.

```auto
#get latest DB info
lastDBvalue = system.db.runNamedQuery("Project", "Read_DB", {"tag_name" : PlcTag})
if ( not ((0 == lastDBvalue.rowCount))):
	lastVal = lastDBvalue.getValueAt(0,'val')
	lastTime = lastDBvalue.getValueAt(0,'t_stamp')
	deltaT = system.date.secondsBetween(lastTime,system.date.now())
		
#large enough change in value to log the change, or minSample time is met
if ((0 == lastDBvalue.rowCount) or (abs(currentValue - lastVal) >= historicalDeadband) or ((minSampleRate > 0) and (deltaT >= minSampleRate))):
	system.db.runNamedQuery("Project", "Store_Tag_Change", {"tag_name":PlcTag,"val":currentValue})

```

I might need to add a `Try: Except:`, but haven't used that much so not sure where to put the `Except:`

Or maybe I need to edit my query:

```auto
SELECT TOP 1 val, t_stamp FROM Data where tag_id=:tag_name order by t_stamp desc

```

Trying to add `IF EXISTS` before the select, I get `SQLServerException: A result set was generated for update. `

```auto
IF EXISTS (select 1 from Data Where tag_id = :tag_name)
	SELECT TOP 1 val, t_stamp FROM Data where tag_id=:tag_name order by t_stamp desc

```

---

<div class="post-metadata">

**Author:** ![amarks](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/amarks/32/45610_2.png) [@amarks](https://forum.inductiveautomation.com/u/amarks)\
**Post date:** [November 11, 2022, 5:17pm UTC](https://forum.inductiveautomation.com/t/handle-named-query-timeout-in-python/66397/2 "2022-11-11T17:17:43Z")

</div>

The reason for the error was I was running it in the database query browser. Running it with `system.db.runQuery()`, I was able to get a result set.

Looks like it'll be a combination of both. Adding the IF EXISTS prevents the query from timing out and using try: except: handles the error thrown when the query does not return a result set.  
  
  
Query:

```auto
IF EXISTS (SELECT 1 FROM Data where tag_id=:tag_name)
	SELECT TOP 1 val, t_stamp FROM Data where tag_id=:tag_name order by t_stamp desc

```

  
Script:

```auto
#get latest DB info
noEntries = 0
try:
	lastDBvalue = system.db.runNamedQuery("Project", "Read_DB",{"tag_name" : PlcTag})
	if ( not ((0 == lastDBvalue.rowCount))):
		lastVal = lastDBvalue.getValueAt(0,'val')
		lastTime = lastDBvalue.getValueAt(0,'t_stamp')
		deltaT = system.date.secondsBetween(lastTime,system.date.now())
except:
	noEntries = 1
			
		
#large enough change in value to log the change
if (((0 == lastDBvalue.rowCount) or (1 == noEntries)) or (abs(currentValue - lastVal) >= historicalDeadband) or ((minSampleRate > 0) and (deltaT >= minSampleRate))):
	system.db.runNamedQuery("Project", "Store_Tag_Change", {"tag_name":PlcTag,"val":currentValue})

```