OUTER JOIN yields wrong results when used with GROUP BY, CASE and COUNT DISTINCT

1. Add file resource adapter in standalone-teiid.xml: <resource-adapter id= "file" > <module slot= "main" id= "org.jboss.teiid.resource-adapter.file" /> <connection-definitions> <connection-definition class-name= "org.teiid.resource.adapter.file.FileManagedConnectionFactory" jndi-name= "java:/files" enabled= "true" pool-name= "files" > <config-property name= "AllowParentPaths" > true </config-property> <config-property name= "ParentDirectory" > C:/testdata </config-property> </connection-definition> </connection-definitions> </resource-adapter> 2. Add MySQL database configuration in standalone-teiid.xml: <datasource jndi-name= "java:/test_dwh_my" pool-name= "test_dwh_my" enabled= "true" use-java-context= "true" > <connection-url> jdbc:mysql://localhost:3306/dwh?zeroDateTimeBehavior=convertToNull </connection-url> <driver> mysql </driver> <new-connection-sql> set SESSION sql_mode = 'ANSI' </new-connection-sql> <pool> <min-pool-size> 2 </min-pool-size> <max-pool-size> 70 </max-pool-size> </pool> <security> <user-name> root </user-name> <password> XXXXXX </password> </security> <validation> <valid-connection-checker class-name= "org.jboss.jca.adapters.jdbc.extensions.mysql.MySQLValidConnectionChecker" /> <exception-sorter class-name= "org.jboss.jca.adapters.jdbc.extensions.mysql.MySQLExceptionSorter" /> </validation> <timeout> <blocking-timeout-millis> 120000 </blocking-timeout-millis> <idle-timeout-minutes> 5 </idle-timeout-minutes> </timeout> </datasource> 3. Add in test-vdb.xml java:/test_dwh_my configured in previous step as datasource: <model name= "dwh_my" > <property name= "importer.useFullSchemaName" value= "false" /> <property name= "importer.tableTypes" value= "TABLE,VIEW" /> <property name= "importer.importKeys" value= "false" /> <source name= "test_dwh_my" translator-name= "mylobs" connection-jndi-name= "java:/test_dwh_my" /> </model> <translator name= "mylobs" type= "mysql5" > <property name= "CopyLobs" value= "true" /> <property name= "SupportsNativeQueries" value= "true" /> </translator> 4. Configure in the test-vdb.xml the following virtual view: <model visible = "true" type = "VIRTUAL" name = "views" > <metadata type = "DDL" > <![CDATA[ create view vLeft as SELECT "csv_table" . "created_at" , "csv_table" . "order_id" , "csv_table" . "store_id" FROM (call files.getFiles( 'test1.csv' )) f, TEXTTABLE(to_chars(f.file, 'UTF-8' ) COLUMNS "created_at" STRING , "order_id" STRING , "store_id" STRING DELIMITER ';' QUOTE '"' HEADER 1 ) "csv_table" ]]> </metadata> </model> 5. Load the data from the other file (test2.csv - attached to this issue) into a MySQL table or a MS SQL table (vRight table name in my case, all fields have varchar types). 6. Run the statement below (rebuy_check column contains no NULLs, that's correct): select count ( a . "order_id" ) anzahl_orders, ( case when b. "order_id" is not null then 'Direct Rebuy' else 'Standard' end ) rebuy_check FROM views.vLeft a left JOIN dwh_my.vRight b on b.order_id= a .order_id group by ( case when b. "order_id" is not null then 'Direct Rebuy' else 'Standard' end ) ;; 7. Add a DISTINCT to the COUNT (rebuy_check column now contains NULLs, that's incorrect): select count ( distinct a . "order_id" ) anzahl_orders, ( case when b. "order_id" is not null then 'Direct Rebuy' else 'Standard' end ) rebuy_check FROM views.vLeft a left JOIN dwh_my.vRight b on b.order_id= a .order_id group by ( case when b. "order_id" is not null then 'Direct Rebuy' else 'Standard' end ) ;; 8. Remove the COUNT entirely (rebuy_check column now contains NULLs, that's incorrect): select ( case when b. "order_id" is not null then 'Direct Rebuy' else 'Standard' end ) rebuy_check FROM views.vLeft a left JOIN dwh_my.vRight b on b.order_id= a .order_id group by ( case when b. "order_id" is not null then 'Direct Rebuy' else 'Standard' end ) ;;