Lossless Decomposition

• If the information is not lost from the relation that is decomposed, then the decomposition will be lossless.
• The result of lossless decomposition after natural joins will be exactly the same relation as it was before the decomposition.

EMPLOYEE_DEPARTMENT table:

EMPLOYEE Table: The above table is decomposed into two relations: EMPLOYEE and DEPARTMENT

Table 01: EMPLOYEE

Table 02: DEPARTMENT

The Above two tables are joined on the common column “EMP_ID.” 

 Employee ⋈ Department

The above table is the original table as it was before decomposition. Hence, the decomposition is Lossless join decomposition.