How to merge two rows into one row in sql?

This type of transformation is known as a pivot. You did not specify what database you are using but you can use an aggregate function with a CASE expression in any system:

select employeeid,  max(case when IsActive = 'true' then IndividualPay end) IndPay_IsActive,  max(case when IsActive = 'false' then IndividualPay end) IndPay_IsNotActive,  max(case when IsActive = 'true' then FamilyPay end) FamilyPay_IsActive,  max(case when IsActive = 'false' then FamilyPay end) FamilyPay_IsNotActivefrom yourtablegroup by employeeid

See SQL Fiddle with Demo

Depending on your database, if you have access to both the PIVOT and UNPIVOT functions, then they can be used to get the result. The UNPIVOT function converts the IndividualPay and FamilyPay columns into rows. Once that is done, then you can create the four new columns with the PIVOT function:

select *from(  select employeeid,    case when isactive = 'true'      then col+'_IsActive'      else col+'_IsNotActive' end col,     value  from yourtable  unpivot  (    value    for col in (IndividualPay, FamilyPay)  ) unpiv) srcpivot(  max(value)  for col in (IndividualPay_IsActive, IndividualPay_IsNotActive,              FamilyPay_IsActive, FamilyPay_IsNotActive)) piv

See SQL Fiddle with Demo.

Both give the same result:

| EMPLOYEEID | INDIVIDUALPAY_ISACTIVE | INDIVIDUALPAY_ISNOTACTIVE | FAMILYPAY_ISACTIVE | FAMILYPAY_ISNOTACTIVE |----------------------------------------------------------------------------------------------------------------|          1 |                    200 |                       100 |                300 |                   150 |

Select    EmployeeID,    Active.IndividualPay As IndPay_IsActive,    Active.FamilyPay As FamilyPay_IsActive,    Inactive.IndividualPay As IndPay_IsNotActive,    Inactive.FamilyPay As FamilyPay_IsNotActiveFrom    PayTable Active    Join PayTable Inactive On Active.EmployeeID = Inactive.EmployeeId        And Inactive.IsActive = 'false'Where    Active.IsActive = 'true'