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Two TZQuery'ies connected via MasterSource

Posted on 2012-03-21
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Last Modified: 2012-03-21
Hello Experts!

I have to TZQuery components.

They are providing data from two Master- Detail tables.

It looks like this:

1.

select * from table1 where index = 1;

2.

select * from table2;

These two TZQuery are connected together via MasterSource, MasterFields, LinkedFields and IndexFieldNames.

It works fine but slowly.

I wonder if I could make it work faster...?

Maybe I should avoid queries like:

select * from table2?

What is the best practice to realize this master- detail connection?

Thank you

panJames
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Question by:panJames
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LVL 37

Expert Comment

by:Geert Gruwez
ID: 37746930
to provide tuning solution, you'll need to indicate what database you are using
in general:
minimize your column list (only select columns you really want)
minimize your rows returned (do you actually read more than 25 lines ?)

for master-detail you can usually combine in 1 query

select
  m.column1 master_col1,
  m.column2 master_col2,
  m.column3 master_col3,
  d.column1 detail_col1,
  d.column2 detail_col2
from table1 m
  left join table2 d on m.mastercolumn = d.mastercolumn
where m.index = 1;

displaying the data in the detail view can be done by applying a filter on the data in memory
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LVL 37

Expert Comment

by:Geert Gruwez
ID: 37746938
when tuning a problem the basics should be checked too:
network > amount of data to copy
local pc > cpu load, memory,
database type > local, server, load
query > optimal execution path ?
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LVL 37

Expert Comment

by:Geert Gruwez
ID: 37746941
delphi is all about code
if you don't supply code, it's mainly guessing where your problem is
0
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Author Comment

by:panJames
ID: 37746999
"minimize your rows returned (do you actually read more than 25 lines ?)"

how do you make your query return only lets say maximum 25 lines?

Thank you

panJames
0
 
LVL 37

Expert Comment

by:Geert Gruwez
ID: 37747003
database type ?
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LVL 37

Expert Comment

by:Geert Gruwez
ID: 37747027
mysql
select columns from table LIMIT 1, 25

oracle
select columns from table where rownum <= 25
> doesn't have a offset

in the properties of some query components you can find this:
FethAll: boolean; (default false)
FetchCount: 25; (default)

some grids like devexpress know this and can call FetchNext to get all data
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LVL 37

Expert Comment

by:Geert Gruwez
ID: 37747072
Zeos lib components don't have this functionality
you'll have to use other components or do it with sql
0
 

Author Comment

by:panJames
ID: 37747079
Firebird
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LVL 37

Accepted Solution

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Geert Gruwez earned 500 total points
ID: 37747115
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