Compare the cost of two different query plans for the following query: Salary < 40000 (EMPLOYEE

Compare the cost of two different query plans for the following query:

σ_{Salary< 40000}(EMPLOYEE ∞ _Dno=DnumberDEPARTMENT)

Use the database statistics shown in Figure 19.6.

Figure 19.6

Transcribed Image Text:

Figure 19.6 Sample statistical information for relations in Q2. (a) Column information. (b) Table information. (c) Index information. (a) Table_name Column_name Num_distinct Low_value High_value PROJECT Plocation 200 200 PROJECT Pnumber 2000 1 2000 PROJECT Dnum 50 1 50 DEPARTMENT Dnumber DEPARTMENT Mgr_ssn 50 1 50 50 1 50 ΕMPLOYEΕ Ssn 10000 1 10000 ΕMPLOYEΕ Dno 50 1 50 EMPLOYEE Salary 500 1 500 (b) Table_name Num_rows Blocks PROJECT 2000 100 DEPARTMENT 50 EMPLOYEE 10000 2000 (c) Index_name Uniqueness Blevel* Leaf_blocks Distinct_keys PROJ_PLOC NONUNIQUE 1 200 EMP_SSN UNIQUE 1 50 10000 EMP SAL NONUNIQUE 1 50 500 *Blevel is the number of levels without the leaf level.