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Explicitly specifying the join condition - SQL
SELECT *
FROM IS_CALLED JOIN IS_ENROLLED_ON
ON ( IS_CALLED.StudentId = IS_ENROLLED_ON.StudentId )
Now, the key word JOIN in all of the foregoing examples can be harmlessly preceded by the word INNER. SQL also supports what are called "outer joins". The outer join of t1 and t2 contains all the rows of the inner join and possibly some more if either operand has rows which fail to participate in the inner join. Such a row might participate in the outer join, accompanied by NULL for each column of the other operand. The key words LEFT, RIGHT, and FULL, each optionally followed by OUTER, are used to specify whether unmatched rows of the first (left) operand, the second (right) operand, or both operands, respectively, are to appear in the result. Example shows an SQL outer join. A single row for student S5 appears in the result, with NULL in place of a value for CourseId.
Manipulating Objects: You can use an object type in the CREATE TABLE statement to indicate the datatype of a column. When the table is created once, you can use the SQL statem
Effects of NULL for union - SQL The treatment of NULL in invocations of EXCEPT is as for UNION. This is different from its treatment in those of NOT IN and quantified compari
Effects of NULL for UNIQUE Specification When a UNIQUE specification u for base table t includes a column c that is not subject to a NOT NULL constraint, the appearance of sev
Expressions An expression is a randomly complex combination of the constants, variables, literals, operators, & function calls. The simplest expression is the single variabl
Use the RETURNING Clause Frequently, the application requires information about the row affected by a SQL operation, for illustration, to produce a report or take a subsequent
CHECK Constraints in SQL A CHECK constraint is a table constraint defined using the key word CHECK, as already illustrated in several examples in this chapter. In particular,
Bulk Fetching The illustration below shows that you can bulk-fetch from a cursor into one or more collections: DECLARE TYPE NameTab IS TABLE OF emp.ename%TYPE; TYPE S
Closing a Cursor The CLOSE statements disable the cursor, and the result set becomes undefined. An illustration of the CLOSE statement as shown: CLOSE c1;
Deriving Predicates from Predicates in SQL The corresponding section in the theory book describes how predicates can be derived from predicates using (a) the logical connectiv
DECLARE : This keyword signals the beginning of the declarative section of the PL/SQL block, that contains local declarations. The Items declared locally exist only within the
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