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PL/SQL provides the functionality of other procedural programming languages, such as decision making, iteration etc. A PL/SQL program unit is one of the following: PL/SQL anonymous block, procedure, function, package specification, package body, trigger, type specification, type body, library. Program units are the PL/SQL source code that is ...
The CASE expression, for example, enables SQL to perform conditional branching within queries, providing a mechanism to return different values based on evaluated conditions. This logic can be particularly useful for data transformation during retrieval, especially in SELECT statements.
The dangling else is a problem in programming of parser generators in which an optional else clause in an if–then(–else) statement can make nested conditional statements ambiguous.
In practice it has been observed that most arithmetic IF statements reference the following statement with one or two of the labels. This was the only conditional control statement in the original implementation of Fortran on the IBM 704 computer. On that computer the test-and-branch op-code had three addresses for those three states.
Title Authors ----- ----- SQL Examples and Guide 4 The Joy of SQL 1 An Introduction to SQL 2 Pitfalls of SQL 1 Under the precondition that isbn is the only common column name of the two tables and that a column named title only exists in the Book table, one could re-write the query above in the following form:
Several other databases (including Microsoft SQL Server, MySQL, PostgreSQL, SQLite, and Teradata) enable one to omit the FROM clause entirely if no table is needed. This avoids the need for any dummy table. ClickHouse has a one-row system table system.one with a single column named "dummy" of type UInt8 and value 0. This table is implicitly ...
user variables, displayable with the DEFINE command and referenceable with one or two cases of a prefixed character (default prefixes: '&' and '&&'). Oracle Corporation calls these variables "substitution variables". Programmers can use them anywhere in a SQL or PL/SQL statement or in SQL Plus commands.
A keyword such as if or while is used during syntax analysis to determine what sort of statement is being considered. Such analysis is much simpler if keywords are either reserved or stropped. Consider the complexity of using contextual analysis in Fortran 77 to distinguish: IF (B) l1,l2 ! two-way branch, where B is a boolean/logical expression