SQL PROGRAMMING STYLE- P22 doc

... 6.2.3 Avoid Redundant Expressions Rationale: Most modern SQL engines are pretty smart. This was not always the case, so older SQL programmers will sometimes add redundant predicates to a ... OR-ed predicates Rationale: The IN() predicate was first introduced in the Pascal programming language. In SQL it has two forms; the list and the subquery. The list form has a comma-separa...

Ngày tải lên: 06/07/2014, 23:20

... specifications were never explained beyond that. He posted a pseudocode program in T -SQL dialect, which would translate into Standard SQL pseudocode something like this: CREATE PROCEDURE TapeFileRoutine() BEGIN ... overwhelming reason is ignorance of SQL and old habits. The cursors in SQL are modeled after tape file semantics, and people know that kind of procedural programmin...

Ngày tải lên: 06/07/2014, 23:20

... predicates or CASE expressions. As an example of a horrible misuse of SQL, Chris White posted a procedure that built dynamic SQL that would then build a report. Aside from the obvious violations ... what you actually want. The other set operations in SQL- 92, EXCEPT [ALL], and INTERSECT [ALL] are not widely available yet. 6.11 Testing SQL When you are first writing a schema, you wi...

Ngày tải lên: 06/07/2014, 23:20

... score means and why it is incremented. In Standard SQL, a comment begins with two dashes ( ) and ends with a new line, because the first SQL engines were on IBM mainframes and used punchcards. ... brackets. They are a better choice. SQL programmers do not like to put comments in their code, not even redundant or useless ones. My guess is that because SQL does a lot of work in one...

Ngày tải lên: 06/07/2014, 23:20

... passes. The most common use of concatenation codes is in keyword lists in the header records of documents in textbases. The author or librarian assigns each article in the system a list of keywords

Ngày tải lên: 06/07/2014, 23:20

... really fast on the current release of my SQL software? A1: Sure, if I want to lose all of the advantages of an abstract data model, SQL set-oriented programming, carry extra data, and destroy ... faster and easy to program. A2: This is an implementation problem that the SQL engine can handle. For example, Teradata is a SQL designed for very large database (VLDB) applications that...

Ngày tải lên: 06/07/2014, 23:20

... the actual problem. Exceptions: If your SQL product supports the SIMILAR TO predicate (a version of grep() based on the POSIX standard in Standard SQL) , then you might consider having a longer ... Table Declaration Rationale: These constraints are not yet well supported in SQL products, but they are legal SQL- 92 syntax. Their predicates involve the entire table as a whole...

Ngày tải lên: 06/07/2014, 23:20

... FONTS, PUNCTUATION, AND SPACING 2.8 Indentation When you have to indent in block-structured 3GL programming languages, use three spaces. A single space is too short to be read as anything but ... mechanical reasons. That became the definition when we moved to electronic terminals. The rule for SQL is that rivers override what we were doing in the old 3GL languages. Rationale:...

Ngày tải lên: 06/07/2014, 23:20

... Rational: SQL allows you to skip some reserved words and to abbreviate others. Try to use the full forms to document the program. This is a good thing in COBOL, and it works in SQL as well. For ... Standard SQL is consistent and clear about aliases, views, and derived tables, as well as a highly orthogonal language. If the UPDATE clause could take an alias, according to the Standar...

Ngày tải lên: 06/07/2014, 23:20

... SECTION | SELECT | SESSION | SESSION_USER | SET | SIZE | SMALLINT | SOME | SPACE | SQL | SQLCODE | SQLERROR | SQLSTATE | SUBSTRING | SUM | SYSTEM_USER | TABLE | TEMPORARY | THEN | TIME | TIMESTAMP ... have to wrap exceptionally long lines. This is not as big a problem in a concise language like SQL as it was in a verbose language like COBOL. 2.1 Typography and Code 29 | MATCH...

Ngày tải lên: 06/07/2014, 23:20