- About
- Services
- Projects
- Blog
- Contact
- About
- Services
- Projects
- Blog
- Contact
Category Archives: SQL
¨ Can use scalar subqueries in WHERE clause comparisons Example: 🞑 Want to find the name of the branch with the smallest number…
Widely used: 🞑 Direct comparison with scalar-subquery results 🞑 Set-membership tests: IN, NOT IN 🞑 Empty-set tests: EXISTS, NOT EXISTS ¨ Less frequently…
¨ Some subqueries produce only a single result SELECT MAX(assets) FROM branch; 🞑 Called a scalar subquery 🞑 Still a relation, just with…
¨ SQL provides broad support for nested subqueries 🞑 A SQL query is a “select-from-where” expression 🞑 Nested subqueries are “select-from-where” expressions embedded…
The HAVING clause can use aggregate functions in its predicate 🞑 It’s applied after grouping/aggregation, so those values are available 🞑 The WHERE…
¨ To apply filtering to the results of grouping and aggregation, use a HAVING clause 🞑 Exactly like WHERE clause, except applied after…
The WHERE clause is applied before any grouping occurs SELECT G1,G2,..., F1(A1),F2(A2),... FROM r1,r2,... WHERE P GROUP BY G1,G2,... 🞑 Translates into relational…
¨ SQL doesn’t require that you specify the grouping attributes in the SELECT clause 🞑 Only requirement is that the grouping attributes are…
¨ Note the difference between relational algebra notation and SQL syntax Relational algebra syntax: G1,G2,…,GnGF1(A1),F2(A2),…,Fm(Am)(E) 🞑 Grouping attributes only appear on left of…
¨ Can group on multiple attributes 🞑 Each group has unique values for the entire set of grouping attributes ¨ Example: “How many…
We continuously strive to develop new software solutions and technologies that address specific needs and challenges. By leveraging their expertise and creativity, we contribute to solving complex problems and improving efficiency across various industries.