Category: APP Development

If the Zim application already exists, then some modifications to the data dictionary definitions for EntitySets and data relationships must be performed. Specifically, the field “EntType” in the data dictionary EntitySet “EntitySets” and/or the field “RelType” in the data dictionary entity set “Relationships” must be flagged as residing on the SQL server. These fields should…
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EntitySets and data relationships in Zim can also be defined to map to SQL “views”. Again, the Zim field list need not include all columns of the view, nor need the field sequence correspond to that of the columns of the view. However, if the corresponding EntitySet or data relationship must be updated, then the…
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The mapping between an SQL table and a Zim EntitySet or data relationship need not be complete with respect to the set of columns owned by the table. Zim retrieves only the columns required from an SQL table; it generates the minimal “select-column-list” to satisfy the requirements of the corresponding Zim command. The Zim Definition…
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Database systems, including Zim, have rules as to how objects such as database tables and columns (EntitySets and fields and Zim) are named. In Zim, object names must be 1 to 18 characters in length and start with an alphabetic character, an underscore (“_”), or dollar sign (“$”). If the name of a SQL table…
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Most SQL servers support the concept that each table is “owned” by a “user” or a “creator”. This enables multiple tables with the same name, but different owners, to be created. These servers also enable users to access tables owned by other users. When a user has some private information stored in database space owned…
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In general, SQL servers support limited indexing capabilities. Indexes can be maintained on individual columns (multi-valued or unique) and also on the concatenation of two or more columns (multi-valued or unique). In Zim terms, an indexed virtual field that corresponds to an SQL concatenated index can be represented only by an expression of the form:…
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Zim supports the specification of decimal places for fields whose internal representation is in the form of integers (data types “int”, “longint” and “vastint”). This is done by maintaining the logical position of the decimal point external to the physical storage of the data. SQL servers do not do this – integer data types contain…
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Indexed Fields in WHERE Clauses In Zim, developers use expressions in the form a. … WHERE >= … b. … WHERE <= … WHERE clauses retrieve data in either (a) ascending or (b) descending sequence of the data values in . This technique is used instead of an explicit sort because it takes advantage of…
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