IF condition in DAX is creating Cartesian Join on rows - powerbi

Question

Dax formula without If condition works fine, but as soon as I add an IF condition rows start multiplying. I believe it's doing Cartesian Product.
My requirement is simple. I need to show only those rows in which Sickness[Start_Date]>LASTDATE(Test[Date])
The complete formula is -
Measure =
var val = CALCULATE(MAX(Sickness[Start_Date]),FILTER(Sickness,Sickness[Start_Date]>LASTDATE(Test[Date])),ALL())
return
IF(val = BLANK(),0,1)
I have 3 separate tables Emp_data, Test and Sickness.
To replicate this scenario, Please follow the below steps:
1st Step : Create table Emp_data
Emp_data = DATATABLE("Emp_no",INTEGER,"Name",STRING,{{101,"A"},
{102,"B"},
{103,"C"},
{104,"D"},
{105,"E"},
{106,"F"},
{107,"G"},
{108,"I"},
{109,"J"},
{110,"K"},
{111,"L"},
{112,"N"},
{113,"M"},
{114,"O"},
{115,"P"},
{116,"Q"},
{117,"R"},
{118,"S"},
{119,"T"},
{120,"U"}
})
create table : Test
Test = DATATABLE("Emp_No",INTEGER,"Date",DATETIME,"Result",INTEGER,{{101,"3/10/2020",1},
{101,"3/13/2020",2},
{102,"3/11/2020",1},
{103,"3/12/2020",2},
{104,"3/13/2020",1},
{105,"3/14/2020",1},
{106,"3/15/2020",2},
{107,"3/16/2020",1},
{108,"4/20/2020",1},
{109,"4/21/2020",2},
{110,"4/22/2020",2},
{111,"4/23/2020",1},
{112,"4/24/2020",1},
{113,"4/25/2020",2},
{114,"4/26/2020",1},
{115,"4/27/2020",2},
{116,"5/5/2020",1},
{117,"5/5/2020",1},
{118,"5/5/2020",1},
{119,"5/5/2020",1},
{120,"5/5/2020",2}
})
Create table Sickness
Sickness = DATATABLE("Emp_no",INTEGER,"Start_Date",DATETIME,"End_Date",DATETIME,"Sickness_Code",INTEGER,{{101,"2/12/2020","2/12/2020",30},
{101,"3/10/2020","3/15/2020",50},
{101,"3/20/2020","3/30/2020",50},
{101,"4/5/2020","4/10/2020",40},
{102,"3/11/2020","3/11/2020",50},
{107,"3/1/2020","3/2/2020",30},
{107,"3/15/2020","3/20/2020",50},
{107,"3/21/2020","3/31/2020",40},
{112,"4/20/2020","4/30/2020",50},
{112,"5/1/2020","5/15/2020",50},
{116,"4/1/2020","4/15/2020",30},
{116,"5/3/2020","5/15/2020",50},
{116,"5/16/2020","5/26/2020",50},
{116,"5/27/2020","5/29/2020",40}}
)
Second Step is to create relationship between these 3 tables. Emp_Data and Test table have one to many relationship. I changed the filter direction to BOTH. Thinking may be this will resolve the issue. Create relation many to many between the tables Test and Sickness. The image is attached
The output is as follows :
If I remove the IF condition my out is what I need :
Can someone help me in understanding this behavior of Power BI. This looks very strange. Why row count is increasing after applying IF condition. Thanks in advance

Answer 1

It's because you assigned a 0 value to all blank values in your Sickness data table. Once your remove the if statement, Power BI only shows data rows that do not return a blank value.
To fix your issue try this updated meassure:
Measure =
VAR val = CALCULATE(MAX(Sickness[Start_Date]),FILTER(Sickness,Sickness[Start_Date]>LASTDATE(Test[Date])),ALL())
VAR OneZero = IF(ISBLANK(val),0,1)
RETURN
IF(HASONEVALUE(Sickness[Emp_no],OneZero)