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Quantification in SQL
To quantify something, as the theory book has it, is to state its quantity, to say how many of it there are. For example, in Tutorial D the expression COUNT(r) denotes the number of tuples in the relation r, to be interpreted as the number of objects represented by those tuples that satisfy a predicate that r is considered to represent. Universal quantification-stating that something is true of all objects under consideration-is involved in expressions such as
Anatomy of a Table: Figure shows the terminology used in SQL to refer to parts of the structure of a table. As you can see, SQL has no official terms for its counterpa
Transaction Visibility As the figure shows, the changes made by an autonomous transaction become visible to another transaction whenever the autonomous transaction commits. Th
%ROWCOUNT When its cursor or cursor variable is opened, the %ROWCOUNT is zeroed. Before the first fetch, the %ROWCOUNT yields 0. Afterward, it yields the number of rows fetche
Ending Transactions A good quality programming practice is to commit or roll back every transaction explicitly. Whether you rollback or issue the commit in your PL/SQL program
Read-Only Operator (+) - SQL The term read-only operator to the mathematical term function. Here I just need to add that the SQL standard reserves the term function for read-
Relational Operators The relational operators permit you to compare randomly complex expressions. The list below provides the meaning of each operator:
Example of Using Aggregation on Nested Tables Example: How many students sat each exam WITH C_ER AS (SELECT CourseId, CAST (TABLE (SELECT DISTINCT StudentId, Mark FROM EXAM
Manipulating Collections Within PL/SQL, the collections add procedural power and flexibility. The biggest benefit is that your program can compute subscripts to process the spec
Main features of PL/SQL A good way to get familiar with PL/SQL is to look at a sample program. The below program processes an order for tennis rackets. At first, it declares a
When Are Constraints Checked Under the model constraints are conceptually checked at all statement boundaries (and only at statement boundaries). By default the same is true
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