Differences between the ABL and SQL in how they display data.
The ABL DISPLAY statement displays data in a tabular format, and sizes it according to the number of columns it fills on the screen or the printed page. The FORMAT of a field determines the maximum number of columns it can occupy without having DISPLAY return an error.
Oracle and MSSQL databases do not allow data records in which the content of a field is larger than the maximum character length. SQL sizes data according to the number of characters it contains. The WIDTH of a field (MAX-WIDTH in the OpenEdge database schema) determines the maximum number of characters it can return to a SQL query without an error being raised.
Much of the time the two approaches will render the same result - the characters in the English alphabet and in many other character sets are normally one column wide, so the number of display columns equals the number of characters in a field. However, there are cases where the results will differ.
Full-width characters
The majority of characters in the CJK (Chinese, Japanese and Korean) character sets are normally rendered as full-width characters, each occupying two columns instead of one. This is not always obvious when they are displayed with proportional fonts, but is clear when a fixed-width font is used.
If a field has a FORMAT of "x(10)" and a MAX-WIDTH of 10, and is populated only with full-width characters, the following differences will be observed:
Composite vs. Base plus Combining characters
The character sets for many languages contain characters embellished with diacritics - u-umlaut (ü), for example. Such characters are often stored as single, composite characters (ü), but they can also be stored as a base character (u) with a column value of 1, followed by the diacritic (¨) as a combining character with a column value of 0.
When a character like ü is stored as a composite character, both the ABL and SQL will treat it in the same way, as a single, one-column character.
If ü is stored as a base character plus a combining character, however, the treatment will be different.
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ABL DISPLAY will combine the characters and assign a column-count of 1.
||1234567890||
|üüüüüüüüüü|
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SQL, while combining the characters for display, will still count them as 2 characters when checking the width of the data in the field.
|üüüüü|
