I have two mysql tables as
Component
+----+-------------------------+--------+
| OldComponentId | NewComponentId |
+----+-------------------------+--------+
| 15 | 85 |
| 16 | 86 |
| 17 | 87 |
+----+-------------------------+--------+
Formulae
+----+-------------------------+--------+
| id | formula_string |
+----+-------------------------+--------+
| 1 | A+15-16+17 |
| 2 | 16+15-17 |
+----+-------------------------+--------+
I want to replace value of formula_string on the basis of NewComponentId as
Formulae
+----+-------------------------+--------+
| id | formula_string |
+----+-------------------------+--------+
| 1 | A+85-86+87 |
| 2 | 86+85-87 |
+----+-------------------------+--------+
I have tried with following mysql query but its not working
update Formulae fr, Component comp set formula_string=REPLACE(fr.formula_string,comp.OldComponentId,comp.NewComponentId).
Please suggest the solutions
thanks.
There is no easy way to do this. As you observed in your update statement, the replacements don't nest. They just replace one at a time.
One thing that you can do is:
update Formulae fr cross join
Component comp
set formula_string = REPLACE(fr.formula_string, comp.OldComponentId, comp.NewComponentId)
where formula_string like concat('%', comp.OldComponentId, '%')
Then continue running this until row_count() returns 0.
Do note that your structure could result in infinite loops (if A --> B and B --> A). You also have a problem of "confusion" so 10 would be replaced in 100. This suggests that your overall data structure may not be correct. Perhaps you should break up the formula into separate pieces. If they are just numbers and + and -, you can have a junction table with the value and the sign for each component. Then your query would be much easier.
Related
Delphi 10.3.3
FireDAC: DBGrid / FDQuery / MySQL
VCL
Hi all,
I have a table with these fields
----------------------
| id | data |
----------------------
| 1 | 0=A;1=B;2=C |
| 2 | 2=Z |
| 3 | |
| 4 | 0=Y;1=X |
| 5 | |
| 6 | |
Each row of data represents only the change in the table
I would like this to be display in a DBGRID:
-----------------------
| id | C0 | C1 | C2 |
-----------------------
| 1 | A | B | C |
| 2 | A | B | Z |
| 3 | A | B | Z |
| 4 | Y | X | Z |
| 5 | Y | X | Z |
| 6 | Y | X | Z |
What I can do for now is only the following table:
-----------------------
| id | C0 | C1 | C2 |
-----------------------
| 1 | A | B | C |
| 2 | | | Z |
| 3 | | | |
| 4 | Y | X | |
| 5 | | | |
| 6 | | | |
To obtain this result, I create additional columns in the event FDQuery1.BeforeOpen
And in the event OnCreateFields, I fill each column but I don't know the previous row content,
So, how can I do to fill in the missing fields in the DBgrid?
Thanks
Franck
I think you mean OnCalcFields, rather than OnCreateFields.
What you need
is certainly possible, either server-side by deriving the necessary values from the prior
row using e.g. a SQL subquery or client-side using calculated fields. This answer is about doing it
client-side.
The problem with doing client-side calculations involving another dataset row is that
to do this you need to be able to move the dataset cursor during the OnCalcFields event. However, at the time, the DataSet will be in either dsCalcFields or dsInternalCalc state
and, while it is, you can't easily move to another row in the dataset. It is possible to do this, but
requires declaring a descendant dataset class (TMyFDQuery) so that you can access the SetTempState
necessary to do revert to the prior state after you've picked up the necessary info from the "other"
row and, if what you need involves more that one field, you need somewhere to store the values temporarily.
So doing it that way gets messy.
A much cleaner approach involves using functional similarity between FireDAC's datasets and TClientDataSets.
One of the nice features of TClientDatasSets is the ease with which you can move the dataset contents between
two CDSs simply by doing
CDS2.Data := CDS1.Data;
FireDAC datasets can do the same trick, but between any FD dataset types. So here is what I would do in your
situation:
Add an FDMemTable to your form/datamodule and copy the query data into it in the FDQuery's AfterOpen event like
this:
procedure TForm2.FDQuery1AfterOpen(DataSet: TDataSet);
begin
FDQuery1.DisableControls;
try
FDMemTable1.Data := FDQuery1.Data;
FDMemTable1.Open;
finally
FDQuery1.First;
FDQuery1.EnableControls;
end;
end;
The FDQuery1.First is to force it to re-do its calculated fields once the FDMemTable data is available
(during the initial FDQuery1.Open, it can't be, of course).
In the FDQuery's OnCalcFields event, use code like this to base the calculated fields'
values on values picked up from the prior row (if there is one of course, the first
row can't hae a "prior" row):
procedure TForm2.FDQuery1CalcFields(DataSet: TDataSet);
begin
if FDMemTable1.Active then begin
if FDMemTable1.Locate('ContactID', FDQuery1.FieldByName('ContactID').AsInteger, []) then begin
FDMemTable1.Prior;
if not FDMemTable1.Bof then begin
// Set FDQuery1's calculated fields that depend on prior row
FDQuery1.FieldByName('PriorRowID').AsInteger := FDMemTable1.FieldByName('ContactID').AsInteger;
end;
end;
end;
end;
In this example, my queried dataset has a ContactID primary key and the calculated value is simply the ContactID value from the prior row. In real life, of course, it
would be more efficient to use persistent field variables rather than keep calling FieldByName.
I suppose another possibility might be to use the CloneCursor method to obtain a lookup cursor
to access the "prior" row, but I've not tried that myself and it may not be possible anyway
(what happens about the calculated fields in the CloneCuror copy?).
I have a special scenario to fetch "unique" row.
Let's say the database is like below
| id | userid | value | others |
|----|--------|-------|---------|
| 1 | 111 | 10 | string1 |
| 2 | 112 | 30 | string2 |
| 3 | 112 | 30 | string3 |
| 4 | 113 | 50 | string4 |
what I want to achieve is to fetch the unique rows based on the "userid" so I'am able to sum all values.
the expect output row can be either id: 1 2 4 or 1 3 4 (both is acceptable for this special case because same id guarantees same value, or in general, get just one row from those row with same userid. ), so the sum will be 90.
Note: DB is extended from Eloquent\model
My old approach is to get DB::unique('userid'); then for each userid DB::where('userid', $id)->value('value'), add the result to sum; I just believe there might be a better approach.
There is Illuminate\Support\Facades\DB in Laravel, it can return the Query Builder. Not recommend to use a model that is named DB.
So just change another name.
By the way, for Eloquent\Model, you can use groupBy and sum too:
Model::groupBy('user_id')->sum('value');
I have two columns in my database that I want to combine before matching them using LIKE statement.
My table:
|---------------------------------|
| ID | PREFIX | SUFFIX |
|---------------------------------|
| 1 | 31 | 523 |
|---------------------------------|
| 2 | 62 | 364 |
|---------------------------------|
I want to be able to supply 315 and ID 1 would be returned. Is there any easy way of doing it? At the moment I am splitting search string and matching separate columns.
Thanks.
SELECT * FROM table WHERE CONCAT(PREFIX, SUFFIX) LIKE '%315%'
I know this question has been asked many times before, but having followed previous solutions I still can't resolve the issue:
I have a SSRS (2008R2) report, that displays data in a matrix. There is a horizontal column group containing values that may or may not exist: when the value doesn't exist, I'd like to replace the empty cell with a 0. Currently the report renders like:
and I'd like those empty cells to have 0's in them instead.
The cell expression was set to:
=Sum(Fields!number.Value)
so I tried
=iif (IsNothing(Sum(Fields!number.Value)),0,Sum(Fields!number.Value))
and
=iif (IsNothing(Fields!number.Value),0,Sum(Fields!number.Value))
and
=iif (Sum(Fields!number.Value)>0,Sum(Fields!number.Value),0)
... but the "empty" cells persist. I'm sure I'm doing something daft... but what?
EDIT: To illustrate my situation better, my query produces output (in SSMS) similar to:
File | outcomeID | number
A | Outcome1 | 2
A | Outcome2 | 1
B | Outcome2 | 2
C | Outcome1 | 1
D | Outcome3 | 2
... which would produce the outcome in SSRS of:
File | Outcome1 | Outcome2 | Outcome3
A | 2 | 1 |
B | 2 | |
C | 1 | |
D | | | 2
using a Column Group:
Even if I change the expression to be simply:
=999
I end up with
File | Outcome1 | Outcome2 | Outcome3
A | 999 | 999 |
B | 999 | |
C | 999 | |
D | | | 999
... i.e. lots of blank spaces.
EDIT2: I've uploaded a very small example .rdl file [REMOVED], using the example data above - it reproduces the issue
my first thought was a change to the stored procedure but since i had a similar report to test something on quickly i had an idea.
try this instead
=0+Sum(Fields!number.Value)
I tend to use the following (on SSRS 2005, however): =CInt(Fields!number.Value). It's possible to use other conversions, like CDbl, as well.
Alternatively, but a tiny bit longer, try =IIf(Fields!number.Value Is Nothing, 0, Fields!number.Value).
I was wondering if there is an easy way of moving some (not all) data from one column to another.
My MySQL table has 200 entries but this is the simplified version of what I am trying to do:
| ID | A | B |
| 1 | | |
| 2 | | |
| 3 | | aa|
| 4 | | bb|
| 5 | | cc|
So I need to get data from column B to Column A but only the ones that have ID greater than (>) 2. so that aa from 3B will go to 3A, bb from 4B will go to 4A...
UPDATE <tablename> SET
A=B,
-- B=''
WHERE ID>2
Might help. The commented-out line needs to be enabled or disabled, depending on whether you want to move or copy the values between columns.