lzexpression
TLzCustomExpression = class(TLz_node);
Expression is widely used in the sql, such as in the where clause,having clause. It's represented by the class TLzCustomExpression, and organized in a binary tree mode.
Usually, expression is created after parsing a sql.
You can also create expression manually in two ways:
1. Create an empty TLzCustomExpression instance, and
than add lexpr, rexpr and set oper yourself.
2. Create a TLzCustomExpression instance with an expression string as paramter, than a binary expression
tree will be created automatically with lexpr, rexpr,
oper and other properties set correctly if input expression string is a valid expression.
You can construct very complex expression by setting lexpr and rexpr to new created TLzCustomExpression instance recursively with proper oper value.
You can create your own function to visit expression in
pre-order(PreOrderTraverse)/in-order(InOrderTraverse)/post-order(PostOrderTraverse).
Here is a list of all expressions type specified by oper:TLzOpType.
Gudu software http://www.sqlparser.com
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