SQL restrictions

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SQL syntax is supported for selection strings.

Table 1 relates the RMC terminology to SQL terminology.
Table 1. Relationship of RMC terminology to SQL terminology
RMC terminology SQL terminology
attribute name column name
selection string WHERE clause
operators predicates, logical connectives
resource class table

Although SQL syntax is generally supported in selection strings, the following restrictions apply.

  • Only a single table may be referenced in an expression.
  • Queries may not be nested.
  • The IS NULL predicate is not supported because there is no concept of a NULL value.
  • The period (.) operator is not a table separator (for example, table.column). Rather, in this context, the period (.) operator is used to separate a field name from its containing structure name.
  • The pound sign (#) is hard-coded as the escape character within SQL pattern strings.
  • All column names are case sensitive.
  • All literal strings must be enclosed in either single or double quotation marks. Bare literal strings are not supported because they cannot be distinguished from column and attribute names.