I started to take a look at the following question: https://stackoverflow.com/questions/8616458/sql-query-like-clarification
Unfortunately it appeared that the original question was somewhat unclear however I decided to interpret this as him trying to only run his query when certain columns in the schema matched his like condition. It's very possible that this wasn't what was being asked however I wanted to challenge myself to do this (posted as a new question since the original was unclear and likely to be deleted and very possible nothing related to this).
What I got to was the following:
select
[OrderID]
,[ProductID]
,[UnitPrice]
,[Quantity]
,[Discount]
from [Northwind].[dbo].[Order Details]
where
(
select top 1
COLUMN_NAME
from INFORMATION_SCHEMA.columns
where COLUMN_NAME like '%ProductID'
) like '%ProductID'
I'm aware how syntactically ridiculous this is however I put it here to give you an idea where my thought process was headed and was also hoping that based on this I could get feedback as to a better method of only running a query when there's a column in the database that matches a condition that you specify? I don't see any purpose for it anywhere - I'm just curious and think I could learn from this.
In SQL, column references must be fixed and known to be valid at the time the query is prepared. It's not legal for the column name to turn out to be invalid in hindsight, after the query begins executing.
The solution given by #Igor gets around this by running two queries, the first to test the system tables and then conditionally run the second. You can't do both in one query.
If I understand you correctly you can do it using system view sys.columns:
IF EXISTS (SELECT 1 FROM sys.columns WHERE name LIKE '%ProductID')
SELECT *
FROM [Northwind].[dbo].[Order Details]
Related
I'm still a bit of a noob, so pardon if this question is a bit obvious. I did search for an answer but either couldn't understand how the answers I found applied, or simply couldn't find an answer.
I have a massive database housed on a DB2 for i server which I'm accessing using SQL through SQLExplorer (based on Squirrel SQL). The tables are very poorly documented and the first order of business is figuring out how to find my way around.
I want to write a simple query that does this:
1) Allows me to search the entire database looking for tables that include a column called "Remarks" (which contains field descriptions).
2) I then want it to search that column for a keyword.
3) I want a table returned that includes the names of the tables that include that keyword (just the name, I can look up the table alphabetically later and look inside if I need to.)
I need this search to be super lightweight, and I'm hoping the concept I describe will achieve that. Anything that eats up a lot of resources will likely anger the sys admin for the server.
Just to show I have tried (and that I am a complete noob), here's what I've got so far.
SELECT *
FROM <dbname>
WHERE Remarks LIKE '<keyword>'
Feel free to mock, I told you I'm an idiot :-).
Any help? Perhaps at least a push in the right direction?
PS - I can't seem to find a search function in SQLExplorer, if someone knows if I can perhaps use a simple search or filter to accomplish this same goal...that would be great.
You can query the system catalog to identify the tables:
SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME
FROM QSYS2.SYSCOLUMNS WHERE UPPER(DBILFL) = 'REMARKS'
And then query each table individually:
SELECT * FROM TABLE_SCHEMA.TABLE_NAME WHERE Remarks LIKE '%<keyword>%'
See the LIKE predicate for details of the pattern expression.
Normally i use something like this
SELECT TABLE_SCHEMA, TABLE_NAME
,COLUMN_NAME,SYSTEM_COLUMN_NAME,COLUMN_HEADING
,DATA_TYPE, "LENGTH",NUMERIC_SCALE
FROM QSYS2.SYSCOLUMNS
WHERE UPPER(COLUMN_NAME) LIKE '%REMARK%'
#JamesA, i'm at V6R1, by default, normal user are not authorized to object QADBIFLD in QSYS
Generally, many if not most IBM i shops (especially those that use RPG) stick to 10 (or less) character schema names & table names, and have a 10 (or less) character names for 'system' column names, even if longer column names are also provided. Column text generally describes each field.
SELECT SYSTEM_TABLE_SCHEMA, SYSTEM_TABLE_NAME
,SYSTEM_COLUMN_NAME,
,DATA_TYPE, "LENGTH",NUMERIC_SCALE
,CHAR(COLUMN_TEXT)
FROM QSYS2.SYSCOLUMNS
WHERE UPPER(COLUMN_NAME) LIKE '%REMARK%'
I've already answered my question but didn't see it on here, so here we go. Please feel free to link to the question if it has been asked exactly.
I simplified my question to the following code:
SELECT 'a' AS col1, 'b' AS col1
Will this give a same column name error?
Will the last value always be returned or is there a chance col1 could be 'a'?
I'm not sure why you would ever want this, but I tried it in Oracle (10g) and it worked fine, returning both columns. I realize you've asked about SQL Server specifically, but I found it interesting that this worked at all.
Edit: It also works on MySQL.
It works in the final query:
However when you do it in a subselect and refer to the ambiguous column aliases in an outer query you get an error:
In SQL 2008 r2 it is valid as a stand alone query. Under certain circumstances it will produce errors (incomplete list):
Inline views
Common Table Entries
Stored Procedures when the output is used by reporting services and presumably similarly integrated tools
It's hard to imagine a case where you would want duplicate row names, and it's easy to think of ways in which writing queries with repeats now could turn sour in the future.
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.
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
I am doing a simple SELECT statement in an Oracle DB and need to select the columns in a somewhat-specific order. Example:
Table A has 100 attributes, one of which is "chapter" that occurs somewhere in the order of columns in the table. I need to select the data with "chapter" first and the remaining columns after in no particular order. Essentially, my statement needs to read something like:
SELECT a.chapter, a. *the remaining columns* FROM A
Furthermore, I cannot simply type:
SELECT a.chapter, a.*
because this will select "chapter" twice.
I know the SQL statement seems simple, but if I know how to solve this problem, I can extrapolate this thought into more complicated areas. Also, let's assume that I can't just scroll over to find the "chapter" column and drag it to the beginning.
Thanks.
You should not select * in a program. As your schema evolves it will bring in things you do not know yet. Think about what happens when someone add a column with the whole book in it? The query you thought would be very cheap suddenly starts to bring in megabytes of data.
That means you have to specify every column you need.
Your best bet is just to select each column explicitly.
A quickie way to get around this would be SELECT a.chapter AS chapterCol, a.* FROM table a; This means there will be one column name chapterCol (assuming there's not a column already there named chapterCol. ;))
If your going to embed the 'SELECT *' into program code, then I would strongly recommend against doing that. As noted by the previous authors, your setting up the code to break if a column is ever added to (or removed from) the table. The simple advice is don't do it.
If your using this in development tools (viewing the data, and the like). Then, I'd recommend creating a view with the specific column order you need. Capture the output from 'SELECT COLUMN_NAME FROM ALL_TAB_COLUMNS' and create a select statement for the view with the column order you need.
This is how I would build your query without having to type all the names in, but with some manual effort.
Start with "Select a.chapter"
Now perform another select on your data base as follows :
select ','|| column_name
from user_tab_cols
where table_name = your_real_table_name
and column_name <> 'CHAPTER';
now take the output from that, in a cut-and-paste manner and append it to what you started with. Now run that query. It should be what you asked for.
Ta-da!
Unless you have a very good reason to do so, you should not use SELECT * in queries. It will break your application every time the schema changes.