OpenEdge中的静态查询与动态查询

Question

问题很常见，让我们从代码可读性、灵活性和性能的角度来看看OpenEdge中每一个问题的优缺点。

静态查询：

+   readability: convenient `buffer.field` notation
+   performance: higher (supposedly, need comments)
-/+ "global scope" allows to handle all previously used buffers, but could lead
                 to ambiguousness, so you'll have to clarify it with a table
                 name (table.field instead of field)
-   flexibility: you cannot alternate predicate-expression much,
                 even IF function is not recommended (can affect performance)      

动态查询：

+   flexibility: you can build predicate-expression completely runtime
+   flexibility: you can work with each field not specifying its name,
                 f.e. you can process all fields of certain record in cycle
+   flexibility: are reusable (need comments on this point)
+/- "local scope" allows to use only buffers specified in `SET-BUFFERS` method
-   readability: a little more code to write
-   performance: slightly slower (not sure)

欢迎增加和更正。以及与任何相关阅读的链接。

Answer 1

静态查询的筛选条件可以“动态”更改，如下所示：

DEFINE QUERY q-name FOR table-name.
DEFINE VARIABLE h-qry   AS HANDLE      NO-UNDO.
h-qry = QUERY q-name:HANDLE.
h-qry:QUERY-PREPARE("for each table-name where table-name.field-name = 1").

从这里开始，查询将与任何普通的静态查询一样处理。

可读性："buffer-handle:buffer-field("field-name"):buffer-value“结构是指动态缓冲区--在动态查询中使用静态缓冲区是完全可以接受的(通过缓冲区表-名称:句柄)，因此动态查询缓冲区可以使用w/静态缓冲区，并且不总是需要使用它的句柄来取消引用字段。

性能:上一次进行比较时，对于相同的查询条件，动态查询比静态查询慢。好处是它们比静态查询更灵活。

可重用性:一旦设置了动态查询的缓冲区结构AFAIK，就不能更改它。但是，可以使用与静态查询相同的新筛选条件重新打开它。