如何用动态"queries"代替静态"query"的工作方式？

Question

在另一个问题中，我问如何处理可能定义或不定义表的情况。我正在尝试遵循的建议解决方案是使用动态"查询"。而不是静态的。不幸的是，我不知道如何做到这一点，有人能帮我吗?让我给你一个例子:

静态工作方式:

FIND Table1 WHERE Table1.field1          = 123
AND Table1.field2        = Current-Table.field2
AND UPPER(Table1.field3) = "Constant-string"
AND Table1.field4        = temp-table.field4 NO-ERROR.
IF NOT AVAILABLE Table1
THEN DO:
CREATE Table1.
ASSIGN Table1.field1 = 123
Table1.field2 = Current-Table.field2
Table1.field3 = "Constant-string"
Table1.field4 = temp-table.field4.
RELEASE Table1.
END.

动态工作方式:

CREATE BUFFER h-Table1 FOR TABLE "Table1" NO-ERROR.
IF VALID-HANDLE(h-Table1)
THEN DO:
L-Found = h-Table1:FIND-FIRST("WHERE Table1.field1 = " + STRING(123) + 
"AND Table1.field2   = " + STRING(Current-Table.field2) +
"AND UPPER(Table1.field3) = 'Constant-string'" + 
"AND Table1.field4 = " + temp-table.field4) NO-ERROR.
IF NOT L-Found
THEN DO:
h-Table1:BUFFER-CREATE("").
END.
ELSE MESSAGE "FOUND".
END.

是BUFFER-CREATE还是其他方法，我应该如何填写参数(如ASSIGN Table1.Field1 = 123)，…?

Answer 1

使用说明:

def var hb as handle no-undo.
create buffer hb for table "mytable".
hb:buffer-create().
assign
hb::myfield = 123
hb::another = "ok"
.
hb:buffer-release()
finally:
delete object hb no-error.
end finally.

注意hb::myfield是

的简写

hb:buffer-field('myfield'):buffer-value

还要注意，当使用动态对象时，您要负责垃圾收集。如果创建了，则需要删除。

动态查找惟一部分:

def var hb     as handle  no-undo.
def var lfound as logical no-undo.
create buffer hb for table 'Table1'.
lfound = hb:find-uniqe(
'where field1 = 123'
+  ' and field2 = ' + quoter( current-table.field2 ) )
+  ' and upper( field3 ) = "constant-string"'
+  ' and field4 = ' + quoter( temp-table.field4 ) 
) no-error.

或使用替代:

lfound = hb:find-unique(
substitute(
'where field1 = &1':u
+  ' and field2 = &2':u
+  ' and upper( field3 ) = &3':u
+  ' and field4 = &4':u,
123,
quoter( current-table.field2 ),
quoter( 'constant-string' ),
quoter( temp-table.field4 )
)
) no-error.

你很快就会想要创建一个查询生成器类/函数来处理创建查询，可能还会处理运行时验证，现在你也负责。