# "Select null" has different outputs from different data sources
**URL:** https://community.dremio.com/t/select-null-has-different-outputs-from-different-data-sources/9263
**Category:** Uncategorized
**Created:** [June 9, 2022, 6:03am UTC](https://community.dremio.com/t/select-null-has-different-outputs-from-different-data-sources/9263 "2022-06-09T06:03:38Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@bigfacewo](https://community.dremio.com/u/bigfacewo)
#### Post date: [June 9, 2022, 6:03am UTC](https://community.dremio.com/t/select-null-has-different-outputs-from-different-data-sources/9263/1 "2022-06-09T06:03:39Z")
Hi.
I found that “select null” has different outputs from different data sources.
First, test to directly upload the parquet file. I name it “orders” here, and then execute the following SQL:
```auto
SELECT null FROM orders group by null
```
The result is correct:
But if the data is in other databases, such as mysql, I test mysql here. I saved the orders table in MySQL as a view of dremio, named orders2. Execute the following SQL:
```auto
SELECT null FROM orders2 group by null
```
I will get the error:
```auto
RuntimeException: cast function for type NULL is not defined.
```
```auto
SYSTEM ERROR: RuntimeException: cast function for type NULL is not defined
SqlOperatorImpl JDBC_SUB_SCAN
Location 0:0:7
SqlOperatorImpl JDBC_SUB_SCAN
Location 0:0:7
Fragment 0:0
[Error Id: c2283bad-1227-45b3-9419-3ea48c374dc2 on localhost:0]
(java.lang.RuntimeException) cast function for type NULL is not defined
com.dremio.common.expression.fn.CastFunctions.getCastFunc():60
com.dremio.exec.expr.ExpressionMaterializationVisitor.visitCastExpression():650
com.dremio.exec.expr.ExpressionMaterializationVisitor.visitCastExpression():84
com.dremio.common.expression.CastExpression.accept():40
com.dremio.exec.expr.ExpressionTreeMaterializer.materialize():112
com.dremio.exec.expr.ExpressionTreeMaterializer.materialize():143
com.dremio.exec.expr.ClassProducerImpl.materializeAndAllowComplex():112
com.dremio.sabot.op.project.ProjectOperator.createSplitterWithExpressions():419
com.dremio.sabot.op.project.ProjectOperator.createSplitterWithExpressions():395
com.dremio.exec.store.CoercionReader.setupProjector():157
com.dremio.exec.store.CoercionReader.newSchema():136
com.dremio.exec.store.CoercionReader.setup():119
com.dremio.sabot.op.scan.ScanOperator.setupReaderAsCorrectUser():311
com.dremio.sabot.op.scan.ScanOperator.setupReader():302
com.dremio.sabot.op.scan.ScanOperator.setup():266
com.dremio.sabot.driver.SmartOp$SmartProducer.setup():563
com.dremio.sabot.driver.Pipe$SetupVisitor.visitProducer():79
com.dremio.sabot.driver.Pipe$SetupVisitor.visitProducer():63
com.dremio.sabot.driver.SmartOp$SmartProducer.accept():533
com.dremio.sabot.driver.StraightPipe.setup():102
com.dremio.sabot.driver.StraightPipe.setup():102
com.dremio.sabot.driver.StraightPipe.setup():102
com.dremio.sabot.driver.StraightPipe.setup():102
com.dremio.sabot.driver.StraightPipe.setup():102
com.dremio.sabot.driver.StraightPipe.setup():102
com.dremio.sabot.driver.StraightPipe.setup():102
com.dremio.sabot.driver.Pipeline.setup():69
com.dremio.sabot.exec.fragment.FragmentExecutor.setupExecution():431
com.dremio.sabot.exec.fragment.FragmentExecutor.run():283
com.dremio.sabot.exec.fragment.FragmentExecutor.access$1600():95
com.dremio.sabot.exec.fragment.FragmentExecutor$AsyncTaskImpl.run():773
com.dremio.sabot.task.AsyncTaskWrapper.run():120
com.dremio.sabot.task.slicing.SlicingThread.mainExecutionLoop():243
com.dremio.sabot.task.slicing.SlicingThread.run():171
```
This is the test data I used:
[orders.zip](https://community.dremio.com/uploads/short-url/zyNMF4TQXXHqQSkvHxXW5ClzKDn.zip) (403.7 KB)
---
### Author:  [@balaji.ramaswamy](https://community.dremio.com/u/balaji.ramaswamy)
#### Post date: [June 22, 2022, 5:19pm UTC](https://community.dremio.com/t/select-null-has-different-outputs-from-different-data-sources/9263/2 "2022-06-22T17:19:15Z")
@bigfacewo In case of MySQL, Dremi owill push down the SQL to Mysql, what is push down look like? Can you send us the profile? or open raw profile, planning, final physical transformation-see the JDBC push down
---
### Author:  [@bigfacewo](https://community.dremio.com/u/bigfacewo)
#### Post date: [June 23, 2022, 1:25am UTC](https://community.dremio.com/t/select-null-has-different-outputs-from-different-data-sources/9263/3 "2022-06-23T01:25:40Z")
@balaji.ramaswamy Here is the profile:
[892d33da-9dfa-4618-9981-def81e2d74b3.zip](https://community.dremio.com/uploads/short-url/4NUWCdWu2xY28zk3B5hSkryV7l0.zip) (11.9 KB)
---
### Author:  [@balaji.ramaswamy](https://community.dremio.com/u/balaji.ramaswamy)
#### Post date: [July 2, 2022, 7:12am UTC](https://community.dremio.com/t/select-null-has-different-outputs-from-different-data-sources/9263/4 "2022-07-02T07:12:56Z")
@bigfacewo null does not have a data type and hence it is failing, can you please try the below SQL
```auto
select cast(null as varchar) as null_string from orders2
```
---
### Author:  [@bigfacewo](https://community.dremio.com/u/bigfacewo)
#### Post date: [July 22, 2022, 9:39am UTC](https://community.dremio.com/t/select-null-has-different-outputs-from-different-data-sources/9263/5 "2022-07-22T09:39:06Z")
@balaji.ramaswamy
