WEEK 3. EE562 Slides and Modified Slides from Database Management Systems, R.Ramakrishnan 1

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1 WEEK 3 EE562 Slides and Modified Slides from Database Management Systems, R.Ramakrishnan 1 Find names of parts supplied by supplier S1 (Book Notation) (using JOIN) SP JOIN P WHERE S# = S1 {PNAME} (SP WHERE S# = S1 ) JOIN P{PNAME} (using TIMES) ( ( SP WHERE S# = S1 ) TIMES ( P{P#, PNAME} ) WHERE SP.P# = P.P#) { PNAME} EE562 Slides and Modified Slides from Database Management Systems, R.Ramakrishnan 2 1

2 Find names of parts supplied S1 (Algebraic operators) (using JOIN π PNAME ( σ S# = S1 ( S SP ) ) π PNAME (σ S# = S1 ( SP ) P ) (using TIMES) ρ (Newtable (SP.P# -->A, P.P# -->B) σ S# = S1 ( SP ) π PNAME ( σ A=B Newtable) ( π P#,PNAME (P) ) ) EE562 Slides and Modified Slides from Database Management Systems, R.Ramakrishnan 3 Find names of suppliers supplying part P2 ( σ P# = P2 ( S SP ) ) ( S σ P# = P2 ( SP ) ) Book Notation: ( ( SP JOIN S ) WHERE P# = P# ( P2 ) ) { SNAME} A more efficient implementation ( ( SP WHERE P# = P# ( P2 ) ) JOIN S ) { SNAME } EE562 Slides and Modified Slides from Database Management Systems, R.Ramakrishnan 4 2

3 Find names of suppliers supplying at least one red part ( σ color = RED ( P ) SP S ) A more efficient solution π SNAME ( (π P# σ color = RED P ) SP ) S ) A query optimizer can find this solution given the first solution! Book Notation (first solution): ( ( ( P WHERE COLOR = COLOR ( RED ) ) JOIN SP ) { S# } JOIN S ) { SNAME } EE562 Slides and Modified Slides from Database Management Systems, R.Ramakrishnan 5 Understanding search and implementing relational algebraic queries Queries involving all semantics Queries involving exclusion type of search (do not etc.) Use divide and set-theoretic operators EE562 Slides and Modified Slides from Database Management Systems, R.Ramakrishnan 6 3

4 Find names of suppliers supplying all parts π SNAME ( (π S#,P# (SP) / π P# ( P ) ) S ) Book Notation: ( ( S { S# } DIVIDEBY P { P# } PER SP { S#, P# } ) JOIN S ) { SNAME} EE562 Slides and Modified Slides from Database Management Systems, R.Ramakrishnan 7 Find supplier numbers for suppliers who supply at least all those parts supplied by supplier S2. π S#,P# (SP) / π P# (σ S# = S2 (SP) ) Book Notation: S { S# } DIVIDEBY ( SP WHERE S# = S# ( S2 ) ) { P# } PER SP { S#, P# } EE562 Slides and Modified Slides from Database Management Systems, R.Ramakrishnan 8 4

5 Find supplier numbers for all pairs of suppliers that are co-located (i.e.located in the same city) Book Notation: ( ( ( S RENAME S# AS SA ) { SA, CITY } JOIN ( S RENAME S# AS SB ) { SB, CITY } ) WHERE SA < SB ) { SA, SB } EE562 Slides and Modified Slides from Database Management Systems, R.Ramakrishnan 9 Find supplier names who do not supply part P2 Is the following query correct? (S { S#, SNAME } JOIN (SP WHERE P#!= P2 )) {SNAME} EE562 Slides and Modified Slides from Database Management Systems, R.Ramakrishnan 10 5

6 Find PNAME that does not come in Red color. Is the following query correct? P WHERE COLOR!= Red {PNAME} EE562 Slides and Modified Slides from Database Management Systems, R.Ramakrishnan 11 Find SNAMES who supply red or green parts Can identify all red or green parts, then find supplier names who supply one of these parts: ρ (TempP,(σ COLOR = RED COLOR = GREEN (P) ) ) (TempP SP S) Can also define TempP using union! (How?) What happens if is replaced by in this query? EE562 Slides and Modified Slides from Database Management Systems, R.Ramakrishnan 12 6

7 Find Snames who supply both red and green parts Previous approach won t work! Must identify suppliers who supply red parts, supplier who supply green parts, then find the intersection ρ (Tempred, π S# ( σ COLOR = RED (P) SP ) ) ρ (Tempgreen, π S# ( σ COLOR = GREEN (P) SP ) ) ( (Tempred Tempgreen) S) EE562 Slides and Modified Slides from Database Management Systems, R.Ramakrishnan 13 Find S# who have office both in LA and Chicago. Is the following query correct? S WHERE CITY = LA AND CITY = CHICAGO {S#} EE562 Slides and Modified Slides from Database Management Systems, R.Ramakrishnan 14 7

8 Find S# who have offices in at least two cities. EE562 Slides and Modified Slides from Database Management Systems, R.Ramakrishnan 15 Other Operators (Aggregate) Count Average Sum Max Min EE562 Slides and Modified Slides from Database Management Systems, R.Ramakrishnan 16 8

9 Summary Unary operators: σ π Set operators: U I - / Aggregate operators: Count, Average, Sum, Max, Min EE562 Slides and Modified Slides from Database Management Systems, R.Ramakrishnan 17 9