1. A plain query

1
1. A plain query

• SELECT "LastName", "FirstName"
• FROM "Students"
• WHERE "Department" 'CS'
• Query Plan
• Query plan text
• "Seq Scan on "Students" (cost0.00..12.88 rows1
  width236)"
• " Filter (("Department")text 'CS'text)"

2
2 A little complex query

• select I."Cid",max("Grade")
• from "Inroll" as I, "Students" as S
• where S."Sid" I."Sid" And S."Department" 'CS'
• group by I."Cid"
• Query Plan

3
3. Nested Query

• select "LastName", "Firstname"
• from "Inroll" as I, "Students" as S
• where S."Sid" I."Sid" and I."Cid" 'CS2223'
  and
• I."Sid" in (select "Sid"
• from "Inroll"
• where "Cid" 'CS4432')
• Query Plan