I am trying to Update a column in my table Inputcounts called concatenate off of a query called InputConcatenates that has a column also called concatenate. I am running an update query with the field name as concatenate the table name as InputCounts and the update to field as [InputConcatenates].[Concatenate]. But every time I run the query it pulls back that 0 records will be updated. Is my syntax wrong possibly?
Update Query SQL:
UPDATE InputCounts INNER JOIN InputConcatenate
ON InputCounts.CONCATENATE = InputConcatenate.CONCATENATE
SET InputCounts.CONCATENATE = [InputConcatenate].[CONCATENATE];
InputConcatenate Query SQL:
SELECT InputCounts.FLEET, InputCounts.AMMs, [FLEET] & [AMMs] AS CONCATENATE
FROM InputCounts;
You reported this query accomplishes what you want ...
UPDATE InputCounts
SET CONCATENATE = [FLEET] & [AMMs]
WHERE CONCATENATE Is Null;
That may be fine. However CONCATENATE is not updated until you execute the UPDATE, and does not get updated (after having previously received a value) in response to changes in FLEET or AMMs
Decide whether CONCATENATE really needs to exist as a field in your table. You could use a query to derive it whenever you need it:
SELECT *, FLEET] & [AMMs] AS CONCATENATE
FROM InputCounts;
With the query, CONCATENATE will always be up to date.
If your database is ACCDB format and your Access version is >= 2010, another possibility is to make CONCATENATE a "calculated field" type in the table's design:
If you prefer CONCATENATE be Null whenever FLEET or AMMs is Null, change the field's Expression property to [FLEET] + [AMMs]
The advantage of a calculated field is that Access automagically updates its value without further effort (like executing an UPDATE) from you.
A disadvantage is that you can't index a calculated field. That means it's not suited for joins, WHERE criteria, ORDER BY, etc. You'll have to decide whether it's a reasonable fit for your application. :-)
Related
I am using a SSIS Data Flow Task to transfer data from one table to another. Column A in Table A contains a number, the last 3 digits of which I want to store in Column B of Table B.
First I'm trying to grab all of the data in Column A and store in a variable via a simple SELECT statement SELECT COLUMN_A FROM TABLE_A. However, the variable stores the statement as a string when I want the result set of the query. I have set the EvaluateAsExpression property to False but to no avail.
Secondly I want to be able to use the result of this query in the Derived Column of my Data Flow to extract the last 3 digits and store the values in Column_B in the destination. The expression I have is:
(DT_STR,3,1252)RIGHT(#User::[VariableName],3)
I want to store this as a string hence the (DT_STR,3,1252) data type.
All I'm getting so far in Column_B of Table_B is is the last 3 characters of the SELECT statement "E_A". There is a lot of useful information on the web including YouTube videos for things like setting file paths and server names as parameters or variables but I can't see many relevant to the specifics of my query.
I have used an Execute SQL Task to insert row counts from flat files but, in this example, I want to use the Derived Column tool instead.
What am i doing wrong? Any help is gratefully appreciated.
I prefer to do all the work in SQL if you aren't doing anything else with that number.
select right(cast(ColA as varchar(20)),3) from tableA
-- you can add another cast if you want it to be an int
use that in an execute sql to result set = single row.
Map that to a variable.
In a derived column in data flow you can set that variable to the new column.
Thanks KeithL thats one solution I will use in future but I found another.
I dropped the variable and in the Expression box of the Transformation Editor did:
(DT_STR,3,1252)RIGHT((DT_STR,3,1252)Column_A,3).
In my question, I failed to cast Column_A from Table_A as a string. The first use of (DT_STR,3,1252) simply sets the destination column as a string so as not to use the same data type as the source which in my case was int.
Its the 2nd use of (DT_STR,3,1252) that actually casts Column_A from int to a string.
I have a text column named data which has value in format
"`set1:val1,val2|set2:val3`"
so I have 2 sets field and n number of value fields in each set. I know this isn't normalized or proper approach to store data but it's a legacy project I can't change the schema now.
Now I need a single query given two values for each sets say val4 and val5 I need my final data field to be
"`set1:val1,val2,val4|set2:val3,val5`"
I'm really not an expert in SQL query so need an update query for above. Note that I will always get only two values for each set and need to append in existing set values.
This is an ugly solution to an ugly problem
UPDATE table
SET data = CONCAT(REPLACE(data,'|',',val4|'), ',val5')
WHERE data = '...'
The REPLACE operation changes set1:val1,val2|set2:val3 to set1:val1,val2,val4|set2:val3, and then the CONACT operation changes that to set1:val1,val2,val4|set2:val3,val5
I have a table that contains all the weeks of the year (using the client's numbering, so Week 1 is in June), and the dates they start. There is a form where they can choose which week they want to look at, so I've used a ComboBox that grabs all the week numbers for which they've entered data in the WeeklyHours table, using
SELECT Format(WeeklyHours.Week,"0") AS Expr1 FROM WeeklyHours GROUP BY WeeklyHours.Week;
This combobox is then supposed to be used as the week filter for a couple queries I've built, using the combobox value as the matching criteria. The problem is that when the form is closed, those queries can't run, and give me the Enter Parameter Value error for the combobox value.
To fix this, I tried to create a new table called SelectedWeek with a single entry called Week_Number. There is then some AfterUpdate code that saves the selected combobox value to the Week_Number field of SelectedWeek.
I then changed the queries to point to [SelectedWeek]![Week_Number], so that the queries will always use whatever the most recently selected week was.
However, I keep getting the Enter Parameter Value error for SelectedWeek!Week_Number, and I can't figure out why.
Any help would be most appreciated.
Thanks,
Joel
Reason the user is prompted for Parameter Value (by the way, it is not an error) is in both cases the Access SQL engine cannot see either referenced values. In first case, the form is closed and in second case column is not properly aligned to a lookup.
In first scenario, simply keep form open which user selects value from combobox when running other queries. Otherwise, all content on form is not callable since it is closed from memory:
SELECT * FROM TableName WHERE weeknumber = Forms!FormName!WeekNumber
In second scenario, use a DLookUp() part of the Domain Function Family.
SELECT * FROM TableName WHERE weeknumber = DLookUp("Week_Number", "SelectedWeek")
And really, domain functions can be generalized as subqueries in SQL:
SELECT * FROM TableName
WHERE weeknumber IN (SELECT Week_Number FROM SelectedWeek)
Even more, you can run a cross join query (tables separated with commas in FROM clause) of the two tables and avoid lookups. Below assumes SelectedWeek is a one-row, one-column table but with the WHERE condition, length is handled and you can explicitly declare columns in either table:
SELECT *
FROM TableName, SelectedWeek
WHERE TableName.weeknumber = SelectedWeek.Week_Number
I have a table which i keep on updating, from the values of other source in my code. The value I update may or may not be same as the value already in the row.
I need some kind of algorithm may be via mysql (db) or otherwise (part of code) so that I later may be able to identify which rows have a changed value.
There is a date modified column which I change. But that will not be a true indicator as it will always be updated. I want a way by which I can determine whether some predefined columns have changed values,
One solution is this: I can do a select query, then compare and update a changed flag in the table. But that seems complex and not for me as I have a table with a lot of records
Another solution might be to save the md5 checksum of the values in a column and while updating compare the previous md5 and current md5 and so on.
I want to know the best solution.
There's a fairly simple way to handle this problem. Let's think of it as managing when a row's timestamp gets updated.
First of all, as I'm sure you know, your table needs a timestamp column with default settings for INSERT and UPDATE. That looks like this if the column is called ts.
ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
Second, you can use an UPDATE query like this to change the values in a row.
UPDATE stock
SET val1 = 'newval1',
val2 = 'newval2',
changed_by = 'current_user_id'
WHERE id = 'id_to_change'
AND NOT (val1 == 'newval1' AND val2 == 'newval2')
The AND NOT clause on the WHERE will prevent the update from taking place unless 'newval1' or 'newval2' would actually provide new values. This works because no rows match the WHERE clause in the update.
When the update is prevented from taking place your automatically set ts column will not change. Neither will the changed_by column be set to the present user's user_id. So, you have the time and user of the most recent genuine change.
Also, many host language interfaces to MySQL have a method call to determine how many rows were affected by a recent UPDATE operation. With this technique, you'll get back zero rows when the row is not updated. That might be convenient for your user interface.
Also, this technique uses a single query, so it's safe if more than one user is trying to update the same row at the same time. There's no need to use a transaction to guarantee that.
(Note that tracking the changed_by user is optional, and will only work if your application can provide the current user's actual id.)
This is reasonably efficient as long as the database search for WHERE id = 'id_to_change' works quickly.
It does require reworking your application's UPDATE queries. But so would any other approach to this problem.
I am working on a stored procedure in MySQL to update a row in a SQL table. What I have is a table where several of the columns are named incrementally. EX: Page_1, Page_2, Page_3....etc.
The data stored in these locations is updated at different times and I have another column to store the number of times the row has been updated. The count variable gets incremented each time the procedure runs and that allows me to utilize it's value in keeping track of where the next update of the data should take place.
From my research I keep finding solutions utilizing "Dynamic SQL." I do not understand how to utilize this to resolve my issue.
I want to pass a variable in to an update statement as the column name.
The code I currently have is as follows.
SET COUNT = COUNT + 1; -- modify count from count column
SET COLUMNLOCATIONVARIABLE = CONCAT('Page_' , COUNT); -- concatenate the count with the column "Prefix"
UPDATE Table
SET COLUMNLOCATIONVARIABLE = INPUTVARIABLE --Use the concatenated statement as the column name and update it with input data
WHERE mainID = INPUTID;
If anyone could explain to me how to pass this variable in as a column name using Dynamic SQL or another solution utilizing non-dynamic SQL I would appreciate it.
Thanks in advance.
This isn't the way to use a database. Create a new table for your Page_* columns, linked to the main table by an identity, with a page number column. Then you can update and include as many pages as you need, addressed by the main identity and the page number.