90 lines
5.7 KiB
HTML
90 lines
5.7 KiB
HTML
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<meta name="DC.Title" content="Normalization" />
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<meta name="abstract" content="Normalization allows you to compare strings that contain combining characters." />
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Normalization </title>
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</head>
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<body id="rbafynormal"><a name="rbafynormal"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Normalization </h1>
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<div><p>Normalization allows you to compare strings that contain combining
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characters.</p>
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<div class="section"><p> Data tagged with a UTF-8 or UTF-16 CCSID can contain combining
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characters. Combining characters allow a resulting character to be composed
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of more than one character. After the first character of the compound character,
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one of many different non-spacing characters such as umlauts and accents can
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follow in the data string. If the resulting character is one that is already
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defined in the character set, normalization of the string results in multiple
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combining characters being replaced by the value of the defined character.
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For example, if your string contained the letter 'a' followed by an '..',
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the string is normalized to contain the single character 'ä'.</p>
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</div>
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<div class="section"><p>Normalization makes it possible to accurately compare strings.
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If data is not normalized, two strings that look identical on the display
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may not compare equal since the stored representation can be different. When
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UTF-8 and UTF-16 string data is not normalized, it is possible that a column
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in a table can have one row with the letter 'a' followed by the umlaut character
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and another row with the combined 'ä' character. These two values are not
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both compare equal in a comparison predicate: WHERE C1 = 'ä'. For this reason,
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it is recommended that all string columns in a table are stored in normalized
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form.</p>
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</div>
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<div class="section"><p>You can normalize the data yourself before inserting or updating
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it, or you can define a column in a table to be automatically normalized by
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the database. To have the database perform the normalization, specify NORMALIZED
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as part of the column definition. This option is only allowed for columns
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that are tagged with a CCSID of 1208 (UTF-8) or 1200 (UTF-16). The database
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assumes all columns in a table have been normalized.</p>
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</div>
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<div class="section"><p>The NORMALIZED clause can also be specified for function and procedure
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parameters. If it is specified for an input parameter, the normalization
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will be done by the database for the parameter value before invoking the function
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or procedure. If it is specified for an output parameter, the clause is not
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enforced; it is assumed that the user's routine code will return a normalized
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value.</p>
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</div>
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<div class="section"><p>The NORMALIZE_DATA option in the QAQQINI file is used to indicate
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whether the system is to perform normalization when working with UTF-8 and
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UTF-16 data. This option controls whether the system will normalize literals,
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host variables, parameter markers, and expressions that combine strings before
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using them in SQL. The option is initialized to not perform normalization.
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This is the correct value for you if the data in your tables and any literal
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values in your applications is always normalized already through some other
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mechanism or never contains characters which will need to be normalized.
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If this is the case, you will want to avoid the overhead of system normalization
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in your query. If your data is not already normalized, you will want to switch
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the value of this option to have the system perform normalization for you. </p>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rbafyussisql.htm" title="A sort sequence defines how characters in a character set relate to each other when they are compared or ordered. Normalization allows you to compare strings that contain combining characters.">Sort sequences and normalization in SQL</a></div>
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</div>
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<div class="relinfo"><strong>Related information</strong><br />
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<div><a href="../rzajq/qryoptf.htm">Change the attributes of your query with the Change Query Attributes (CHGQRYA) command</a></div>
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</div>
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</div>
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</body>
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</html> |