In an Oracle database, in table A, there is a clob field called 'ID_CLOB', storing some id's from another table B.
Example:
| ID_CLOB |
,15,16,17,18,19,21,23,24,25,30,32,33,
And here is my question, how can I know from a SQL statement to tell if a number, say 15, is in the 'ID_CLOB' field?
Thanks in advcance.
The situation:
I am actually working on a third party application that come with this db schema. Think about the scenario: that in table B, there are person information per line, and table A, let's assume its a department table, each row is a department and the clob field is used to store the information of who are in that department.
If the format of the data in that field is guaranteed to have comma delimiters before and after each value with no spaces, then the POSITION scalar would find it:
SELECT * FROM A
WHERE POSITION( ',15,', in id_clob ) > 0;
This is not very efficient, though, and is fragile. If there are spaces between the values and the commas or if the first value is not preceded by a comma or if the last value is not trailed by a comma, it will fail.
As others have pointed out, it would be better (if you can) to change the database design. In the real world, though, that is not always possible.
i would suggest building a new table -
person_department
-----------------
person_id
department_id
and struggle through the one time parsing of your badly formatted data and put it into this structure.
then you can query easily.
Instead of thinking of a query for your problem you should rather redesign your DB. Your structure violates the 1st normalisation form of database design.
Related
I'm having a table with an id and a name.
I'm getting a list of id's and i need their names.
In my knowledge i have two options.
Create a forloop in my code which executes:
SELECT name from table where id=x
where x is always a number.
or I'm write a single query like this:
SELECT name from table where id=1 OR id=2 OR id=3
The list of id's and names is enormous so i think you wouldn't want that.
The problem of id's is the id is not always a number but a random generated id containting numbers and characters. So talking about ranges is not a solution.
I'm asking this in a performance point of view.
What's a nice solution for this problem?
SQLite has limits on the size of a query, so if there is no known upper limit on the number of IDs, you cannot use a single query.
When you are reading multiple rows (note: IN (1, 2, 3) is easier than many ORs), you don't know to which ID a name belongs unless you also SELECT that, or sort the results by the ID.
There should be no noticeable difference in performance; SQLite is an embedded database without client/server communication overhead, and the query does not need to be parsed again if you use a prepared statement.
A "nice" solution is using the INoperator:
SELECT name from table where id in (1,2,3)
Also, the IN operator is syntactic sugar built for exactly this purpose..
SELECT name from table where id IN (1,2,3,4,5,6.....)
Hoping that you are getting the list of ID's on which you have to perform a query for names as input temp table #InputIDTable,
SELECT name from table WHERE ID IN (SELECT id from #InputIDTable)
I'm trying to put all the below in a single stored procedute that returns a single row because the data is up on Sql Azure and the rule for it is do everything in a single query with a single return.
I have the following tables:
Person (
PersonId
FirstName
...
)
CompanyDomains (
CompanyId
EmailDomain
)
Company (
CompanyId
CompanyName
Billing_PersonId
Admin_PersonId
...
)
I have two problems here. The first is I want to get all the elements of a Company row, and the 2 Person rows of data. That's easy with a join. But the columns for the 2 person columns will have duplicate names. I can do 'as' one by one, which is a pain as the database schema is still in a state of flux. Is there a global way to apply 'as' so all the columns brought in from Billing_PersonId get a Billing_ prepended to the column name and Admin_ prepended to the admin column name?
The second is there is a 1->N list of company domains. Is there a way to pull all those and add a column that is a single string that has "domain1;domain2;" in it? We have the distinct domains in the CompanyDomain table so we can quickly find the company that owns any domain. But a single string works fine when I'm reading the company in.
I know single SQL selects pretty well. But I've got very little experience with stored procedures (aside from calling them) and so what I'm asking here may be basic. If so, sorry. And again, this is for Sql Azure.
thanks - dave
If you are using Azure, then you application should be able to parse XML.
Write a stored procedure to join the three tables, select the data given an input like company id, and return an xml record containing information from all three.
Look at the following references.
FOR XML
http://msdn.microsoft.com/en-us/library/ms178107.aspx
CREATE PROCEUDRE
http://msdn.microsoft.com/en-us/library/ms187926.aspx
If you need more help, you need to post a simple schema with sample data.
USE MY EXAMPLE BELOW FOR SCHEMA + DATA
sql select a field into 2 columns
1 - Without detailed information, not one will be able to help you.
2 - Try it on your own. I can give you the answer but you will not learn anything.
Sincerely
John
I have a table (a) that contains imported data, and one of the values in that table needs to be joined to another table (b) based on that value. In table b, sometimes that value is in a comma separated list, and it is stored as a varchar. This is the first time I have dealt with a database column that contains multiple pieces of data. I didn't design it, and I don't believe it can be changed, although, I believe it should be changed.
For example:
Table a:
column_1
12345
67890
24680
13579
Table b:
column_1
12345,24680
24680,67890
13579
13579,24680
So I am trying to join these table together, based on this number and 2 others, but when I run my query, I'm only getting the one that contain 13579, and none of the rest.
Any ideas how to accomplish this?
Storing lists as a comma delimited data structure is a sign of bad design, particularly when storing ids, which are presumably an integer in their native format.
Sometimes, this is necessary. Here is a method:
select *
from a join
b
on ','+b.column_1+',' like '%,'+cast(a.column_1 as varchar(255))+',%'
This will not perform particularly well, because the query will not take advantage of any indexes.
The idea is to put the delimiter (,) at the beginning and end of b.column_1. Every value in the column then has a comma before and after. Then, you can search for the match in a.column_1 with commas appended. The commas ensure that 10 does not match 100.
If possible, you should consider an alternative way to represent the data. If you know there are at most two values, you might consider having two columns in a. In general, though, you would have a "join" table, with a separate row for each pair.
I have an array of 50+ elements that dictates how many hours were worked for a given week.
What is the proper way to store this information into a database table?
My initial idea was to use a delimiter, but the text is too large (280 characters) to fit.
Additionally, there seems something "wrong" with creating a table column for each element.
Ideas?
Array using delimiter (comma):
37.5,37.5,37.5,37.5,37.5,37.5,37.5,37.5,37.5,37.5, ...
The "proper" way is to store the array's contents as multiple rows in a whole other table, each with a foreign key referencing the record they belong to back in the first table. There may be other things that work for you, though.
[EDIT]: From the details you added I'm guessing your array elements consist of a number of hours worked each week and you have 50+ of them because a year has 52-ish weeks. So what I think you're looking for, is I guess that your current (main) table is called something like "employees," is that each row there should have some unique identifier for each employee record. So your new table might be called "work_weeks" and consist of something like employee_id (which matches the employee id in the current table), week_number, and hours_worked.
Seems like a 1 to many relationship. For this example, tableA is the 1 and tableBlammo is the many.
tableA => column blammoId
tableBlammo => column blammoId, column data
One row in tableA joins to multiple rows in tableBlammo via the blammoId column.
Each row in tableBlammo has one element of the array in the data column.
I have a table, and there is no column which stores a field of when the record/row was added. How can I get the latest entry into this table? There would be two cases in this:
Loop through entire table and get the largest ID, if a numeric ID is being used as the identifier. But this would be very inefficient for a large table.
If a random string is being used as the identifier (which is probably very, very bad practise), then this would require more thinking (I personally have no idea other than my first point above).
If I have one field in each row of my table which is numeric, and I want to add it up to get a total (so row 1 has a field which is 3, row 2 has a field which is 7, I want to add all these up and return the total), how would this be done?
Thanks
1) If the id is incremental, "select max(id) as latest from mytable". If a random string was used, there should still be an incremental numeric primary key in addition. Add it. There is no reason not to have one, and databases are optimized to use such a primary key for relations.
2) "select sum(mynumfield) as total from mytable"
for the last thing use a SUM()
SELECT SUM(OrderPrice) AS OrderTotal FROM Orders
assuming they are all in the same column.
Your first question is a bit unclear, but if you want to know when a row was inserted (or updated), then the only way is to record the time when the insert/update occurs. Typically, you use a DEFAULT constraint for inserts and a trigger for updates.
If you want to know the maximum value (which may not necessarily be the last inserted row) then use MAX, as others have said:
SELECT MAX(SomeColumn) FROM dbo.SomeTable
If the column is indexed, MSSQL does not need to read the whole table to answer this query.
For the second question, just do this:
SELECT SUM(SomeColumn) FROM dbo.SomeTable
You might want to look into some SQL books and tutorials to pick up the basic syntax.