RWDBCriterion

Module:  DB Interface Module   Group:  Expression Classes

RWDBCriterion  RWDBExpr

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RWDBCriterion()

#include <rw/db/expr.h>

RWDBCriterion is the result of applying logical operators to RWDBExpr. It is used to encapsulate SQL WHERE clauses.

RWDBCriterion represents a specialized type of RWDBExpr that is evaluated in an SQL statement as a boolean value. RWDBCriterion adds neither components nor member functions to the base class. Instead, it insures that a nonboolean expression is not placed in a context that requires a boolean expression during compilation.

In this example, an RWDBCriterion is created anonymously to be used as part of an SQL WHERE clause:

int x = somevalue;
RWDBSelector select = myDbase.selector();
select.where(myTable["myColumn"] != x);

RWDBCriterion();

The default constructor creates an empty criterion.

RWDBCriterion(const RWDBExpr& Left, 
              RWDBPhraseBook::RWDBPhraseKey op, 
              const RWDBExpr& Right);

Creates a dyadic RWDBCriterion from the Left and Right operands connected by the logical operator op.

RWDBCriterion(RWDBPhraseBook::RWDBPhraseKey op,
              const RWDBExpr& expr);

Creates a monadic RWDBCriterion from the given op and expr.

RWDBCriterion is a special case of RWDBExpr. Please see RWDBExpr for details about RWDBCriterion usage, including operators and constructors.

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