问题
Question is very common, let's see pros and cons of each in OpenEdge in terms of code readability, flexibility and performance off course.
Static queries:
+ 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)
Dynamic queries:
+ 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)
Additions and corrections are welcome. As well as links to any related read.
回答1:
A static query's filter condition can be changed "on the fly" like so:
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").
from here the query is treated the same as any normal static query.
readability: the "buffer-handle:buffer-field("field-name"):buffer-value" construct refers to dynamic buffers - it's perfectly acceptable to use static buffers in dynamic queries (via the BUFFER table-name:HANDLE), so dynamic query buffers can be used w/static buffers and it's not always necessary to de-reference a field using it's handle.
performance: last time I did a comparison, dynamic queries were slower than static queries for the same query condition. The upside is they're more flexible than static queries.
reusability: Once a dynamic query's buffer structure has been set, AFAIK, it can't be changed. It can be re-opened with a new filter condition same as a static query though.
来源：https://stackoverflow.com/questions/18267870/static-vs-dynamic-queries-in-openedge