Any idea how to create this function in t-sql?
Pseudo-code:
function( #table, #table_column )
{
update #table
set #table_column = replace(#table_column,',','')
where #table_column like '%,%'
}
Ideas I've tried:
Procedures: only take readonly tables (http://technet.microsoft.com/en-us/library/ms187926.aspx)
Functions: cannot do updates...
Any suggestions? Thanks everyone!
Update: I had a database with about 40 tables, each with columns that I needed to remove special characters (i.e., ","). Although it would be nice to create a function/procedure where I could give it the name and fix the column, I decided instead (based on the comments) to just write each update out. Perhaps I was just looking for too fancy of a solution to a relatively simple problem.
The only way to do this is dynamic SQL. Unless you are writing database tools, you rarely need to do this kind of thing. Are you sure your database is designed correctly? What is the problem you are trying to solve?
Why do you need a function?
Usually functions are applied to a column inside the select list, such as SELECT MYFUNC(COL1) FROM TAB1;
This can definitely be done in a Stored Procedure with dynamic SQL. You can even look at a return value for the number of rows updated.
I guess the main question is what is your business requirements??
Related
Thank you for checking my question out!
I'm trying to write a query for a very specific problem we're having at my workplace and I can't seem to get my head around it.
Short version: I need to be able to target columns by their name, and more specifically by a part of their name that will be consistent throughout all the columns I need to combine or compare.
More details:
We have (for example), 5 different surveys. They have many questions each, but SOME of the questions are part of the same metric, and we need to create a generic field that keeps it. There's more background to the "why" of that, but it's pretty important for us at this point.
We were able to kind of solve this with either COALESCE() or CASE statements but the challenge is that, as more surveys/survey versions continue to grow, our vendor inevitably generates new columns for each survey and its questions.
Take this example, which is what we do currently and works well enough:
CASE
WHEN SURVEY_NAME = 'Service1' THEN SERV1_REC
WHEN SURVEY_NAME = 'Notice1' THEN FNOL1_REC
WHEN SURVEY_NAME = 'Status1' THEN STAT1_REC
WHEN SURVEY_NAME = 'Sales1' THEN SALE1_REC
WHEN SURVEY_NAME = 'Transfer1' THEN Null
ELSE Null
END REC
And also this alternative which works well:
COALESCE(SERV1_REC, FNOL1_REC, STAT1_REC, SALE1_REC) as REC
But as I mentioned, eventually we will have a "SALE2_REC" for example, and we'll need them BOTH on this same statement. I want to create something where having to come into the SQL and make changes isn't needed. Given that the columns will ALWAYS be named "something#_REC" for this specific metric, is there any way to achieve something like:
COALESCE(all columns named LIKE '%_REC') as REC
Bonus! Related, might be another way around this same problem:
Would there also be a way to achieve this?
SELECT (columns named LIKE '%_REC') FROM ...
Thank you very much in advance for all your time and attention.
-Kendall
Table and column information in Db2 are managed in the system catalog. The relevant views are SYSCAT.TABLES and SYSCAT.COLUMNS. You could write:
select colname, tabname from syscat.tables
where colname like some_expression
and syscat.tabname='MYTABLE
Note that the LIKE predicate supports expressions based on a variable or the result of a scalar function. So you could match it against some dynamic input.
Have you considered storing the more complicated properties in JSON or XML values? Db2 supports both and you can query those values with regular SQL statements.
I'm building an abstract gem. i need a sql query that looks like this
SELECT * FROM my_table WHERE * LIKE '%my_search%'
is that possible?
edit:
I don't care about querys performance because it's a feature function of a admin panel, which is used once a month. I also don't know what columns the table has because it's so abstract. Sure i could use some rails ActiveRecord functions to find all the columns but i hoped to avoid adding this logic and just using the *. It's going to be a gem, and i can't know what db is going to be used with it. Maybe there is a sexy rails function that helps me out here.
As I understand the question, basically you are trying to build a sql statement which should check for a condition across all columns in that table. A dirty hack, but this generates the required Sql.
condition_string = MyTable.column_names.join(' LIKE ? OR ')
MyTable.all(:conditions => [condition_string, '%my_search%'])
However, this is not tested. This might work.
* LIKE '...' isn't valid according to the SQL standards, and not supported by any RDBMS I'm aware of. You could try using a function like CONCAT to make the left argument of LIKE, though performance won't be good. As for SELECT *, it's generally something to be avoided.
No, SQL does not support that syntax.
To search all columns you need to use procedures or dynamic SQL. Here's another SO question which may help:
SQL: search for a string in every varchar column in a database
EDIT: Sorry, the question I linked to is looking for a field name, not the data, but it might help you write some dynamically SQL to build the query you need.
You didn't say which database you are using, as there might be a vendor specific solution.
Its only an Idea, but i think it worth testing!
It depends on your DB you can get all Columns of a table, in MSSQL for example you can use somethink like:
select name from syscolumns where id=object_id('Tablename')
Under Oracle guess its like:
select column_name from USER_TAB_COLUMNS where TABLE_NAME = 'Tablename'
and then you will have to go through these columns usign a procedure and maby a cursor so you can check for each Column if the data your searching for is in there:
if ((select count(*) from Tablename where Colname = 'searchingdata') > 0)
then keep the results in a separated table(ColnameWhereFound, RecNrWhereFound).
The matter of Datatye may be an Issue if you try to compare strings with numbers, but if you notice for instance under SQL-Server the syscolumns table contains a column called "usertype" which contains a number seems to refer to the Datatype stored in the Columne, like 2 means string and 7 means int, and 2 means smallint, guess Oracle would have something similar too.
Hope this helps.
I got a table with 75 columns,. what is the sql statement to display only the columns with values in in ?
thanks
It's true that a similar statement doesn't exist (in a SELECT you can use condition filters only for the rows, not for the columns). But you could try to write a (bit tricky) procedure. It must check which are the columns that contains at least one not NULL/empty value, using queries. When you get this list of columns just join them in a string with a comma between each one and compose a query that you can run, returning what you wanted.
EDIT: I thought about it and I think you can do it with a procedure but under one of these conditions:
find a way to retrieve column names dynamically in the procedure, that is the metadata (I never heard about it, but I'm new with procedures)
or hardcode all column names (loosing generality)
You could collect column names inside an array, if stored procedures of your DBMS support arrays (or write the procedure in a programming language like C), and loop on them, making a SELECT each time, checking if it's an empty* column or not. If it contains at least one value concatenate it in a string where column names are comma-separated. Finally you can make your query with only not-empty columns!
Alternatively to stored procedure you could write a short program (eg in Java) where you can deal with a better flexibility.
*if you check for NULL values it will be simple, but if you check for empty values you will need to manage with each column data type... another array with data types?
I would suggest that you write a SELECT statement and define which COLUMNS you wish to display and then save that QUERY as a VIEW.
This will save you the trouble of typing in the column names every time you wish to run that query.
As marc_s pointed out in the comments, there is no select statement to hide columns of data.
You could do a pre-parse and dynamically create a statement to do this, but this would be a very inefficient thing to do from a SQL performance perspective. Would strongly advice against what you are trying to do.
A simplified version of this is to just select the relevant columns, which was what I needed personally. A quick search of what we're dealing with in a table
SELECT * FROM table1 LIMIT 10;
-> shows 20 columns where im interested in 3 of them. Limit is just to not overflow the console.
SELECT column1,column3,colum19 FROM table1 WHERE column3='valueX';
It is a bit of a manual filter but it works for what I need.
In the process of fixing a poorly imported database with issues caused by using the wrong database encoding, or something like that.
Anyways, coming back to my question, in order to fix this issues I'm using a query of this form:
UPDATE table_name SET field_name =
replace(field_name,’search_text’,'replace_text’);
And thus, if the table I'm working on has multiple columns I have to call this query for each of the columns. And also, as there is not only one pair of things to run the find and replace on I have to call the query for each of this pairs as well.
So as you can imagine, I end up running tens of queries just to fix one table.
What I was wondering is if there is a way of either combine multiple find and replaces in one query, like, lets say, look for this set of things, and if found, replace with the corresponding pair from this other set of things.
Or if there would be a way to make a query of the form I've shown above, to run somehow recursively, for each column of a table, regardless of their name or number.
Thank you in advance for your support,
titel
Let's try and tackle each of these separately:
If the set of replacements is the same for every column in every table that you need to do this on (or there are only a couple patterns), consider creating a user-defined function that takes a varchar and returns a varchar that just calls replace(replace(#input,'search1','replace1'),'search2','replace2') nested as appropriate.
To update multiple columns at the same time you should be able to do UPDATE table_name SET field_name1 = replace(field_name1,...), field_name2 = replace(field_name2,...) or something similar.
As for running something like that for every column in every table, I'd think it would be easiest to write some code which fetches a list of columns and generates the queries to execute from that.
I don't know of a way to automatically run a search-and-replace on each column, however the problem of multiple pairs of search and replace terms in a single UPDATE query is easily solved by nesting calls to replace():
UPDATE table_name SET field_name =
replace(
replace(
replace(
field_name,
'foo',
'bar'
),
'see',
'what',
),
'I',
'mean?'
)
If you have multiple replaces of different text in the same field, I recommend that you create a table with the current values and what you want them replaced with. (Could be a temp table of some kind if this is a one-time deal; if not, make it a permanent table.) Then join to that table and do the update.
Something like:
update t1
set field1 = t2.newvalue
from table1 t1
join mycrossreferncetable t2 on t1.field1 = t2.oldvalue
Sorry didn't notice this is MySQL, the code is what I would use in SQL Server, my SQL syntax may be different but the technique would be similar.
I wrote a stored procedure that does this. I use this on a per database level, although it would be easy to abstract it to operate globally across a server.
I would just paste this inline, but it would seem that I'm too dense to figure out how to use the markdown deal, so the code is here:
http://www.anovasolutions.com/content/mysql-search-and-replace-stored-procedure
Does anyone have a good method for searching an entire database for a given value?
I have a specific string I'm looking for, it's in TableA, and it's also a FK to some other table, TableB, except I don't know which table/column that is.
Assuming there's a jillion tables and I don't want to look through them all, and maybe will have to do this in several different cases, what would be the best way?
Since I didn't want a Code-SQL bridge, my only all-SQL idea was:
select tablename and column_name from INFORMATION_SCHEMA.COLUMNS
...then use a cursor to flip through all the columns, and for all the datatypes of nvarchar I would execute dynamic SQL like:
SELECT * from #table where #column = #myvalue
Needless to say, this is slow AND a memory hog.
Anyone got any ideas?
Dump the database and grep?
I guess a more focused question might be: if you don't know how the schema works, what are you going to do with the answer you get anyway?
Here are a couple of links talking about how to do this:
http://blogs.lessthandot.com/index.php/DataMgmt/DataDesign/the-ten-most-asked-sql-server-questions--1#2
http://vyaskn.tripod.com/search_all_columns_in_all_tables.htm
Both of them use the approach you were hoping to avoid. Refine them so that they only searched columns that were foreign keys should improve their performance by eliminating the searching of unnecessary tables.
Here's a solution I wrote several years ago:
http://www.users.drew.edu/skass/sql/SearchAllTables.sql.txt
Just make SP that searches in all relevant columns using OR.
Why don't you know which columns to search on?
If the list of columns is ever-shifting, then you just need to make sure that whatever process results in changing the schema would result in the change in this stored procedure.
If the list of the columns is just too dang big for you to type up inot the SP, use some elementary perl/grep/whatnot to do it in 1 line, e.g for SYBASE.
my_dump_table_schema.pl|egrep "( CHAR| VARCHAR)"|awk '{$1}'|tr "\012" " "|perl -pe '{s/ / = \#SEARCH_VALUE OR /g}'; echo ' = #SEARCH_VALUE'
The last echo is needed to add the value to last column
to dump your data, read up on the bcp Utility