TAILIEUCHUNG - SQL PROGRAMMING STYLE- P25

SQL PROGRAMMING STYLE- P25:Im mot trying to teach you to program in SQL in this book. You might want to read that again. If that is what you wanted, there are better books. This ought to be the second book you buy, not the first. I assume that you already write SQL at some level and want to get better at it. If you want to learn SQL programming tricks, get a copy of my other book, SQL for Smarties (3rd edition, 2005). | Multiple Character Sets 97 I was amazed to go to a major hospital in Los Angeles in mid-1993 and see the clerk still looking up codes in a dog-eared looseleaf notebook instead of bringing them up on her terminal screen. The hospital was still using an old IBM mainframe system which had dumb 3270 terminals rather than a client server system with workstations. There was not even a help screen available to the clerk. The translation tables can be downloaded to the workstations in a client server system to reduce network traffic. They can also be used to build picklists on interactive screens and thereby reduce typographical errors. Changes to the codes are thereby propagated in the system without anyone having to rewrite application code. If the codes change over time the table for a code should have to include a pair of date effective fields. This will allow a data warehouse to correctly read and translate old data. Multiple Character Sets Some DBMS products can support ASCII EBCDIC and Unicode. You need to be aware of this so you can set proper collations and normalize your text. The predicate string IS NOT NORMALIZED in SQL-99 determines if a Unicode string is one of four normal forms . D C KD and KC . The use of the words normal form here is not the same as in a relational context. In the Unicode model a single character can be built from several other characters. Accent marks can be put on basic Latin letters. Certain combinations of letters can be displayed as ligatures ae becomes s . Some languages such as Hangul Korean and Vietnamese build glyphs from concatenating symbols in two dimensions. Some languages have special forms of one letter that are determined by context such as the terminal sigma in Greek or accented u in Czech. In short writing is more complex than putting one letter after another. The Unicode standard defines the order of such constructions in their normal forms. You can still produce the same results with different orderings and .

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