We have a table on the SQL Server 2008 which gets populated by various stored procedures. The problem is that the authors of these stored procedures used some poor choice in code and populated this table using the following syntax:
INSERT INTO persistant_table
SELECT *
FROM #temp_table_with_data
Basically they would create a #temp_table_with_data in the script and the columns would be in the same order and with the same name as they are in the persistant_table.
Now I need to add another column to this persistant_table, but if I do that, I will break all the stored procedures.
Is there a way for me to add a column to this table without breaking all the stored procedures? (In the long run, we will change the stored procedures).
Thank you
No I think.select * will pick all columns and column number should match.
I don't think it's big effort to change the line to have particular columns only or select statement to have default value for column or null and then * to store into columns sequentially. But at least 1 line to be changed
The "ALTER TABLE" is a SQL statement that allows you to make datatype changes to a database table (i.e. change datatype as well as Size columns from an existing table).
ALTER TABLE TableName ALTER COLUMN ColumnName NVARCHAR(200)
You cannot do it without affecting old scripts. This is why 'SELECT *' is not good practice. You'd better create new scripts with explicit column names like
SELECT column1, column2 ....
Related
How do I drop a few tables (e.g. 1 - 3) using the output of a SELECT statement for the table names? This is probably standard SQL, but specifically I'm using Apache Impala SQL accessed via Apache Zeppelin.
So I have a table called tables_to_drop with a single column called "table_name". This will have one to a few entries in it, each with the name of another temporary table that was generated as the result of other processes. As part of my cleanup I need to drop these temporary tables whose names are listed in the "tables_to_drop" table.
Conceptually I was thinking of an SQL command like:
DROP TABLE (SELECT table_name FROM tables_to_drop);
or:
WITH subquery1 AS (SELECT table_name FROM tables_to_drop) DROP TABLE * FROM subquery1;
Neither of these work (syntax errors). Any ideas please?
even in standard sql this is not possible to do it the way you showed.
in standard sql usually you can use dynamic sql which impala doesn't support.
however you can write an impala script and run it in impala shell but it's going to be complicated for such task, I would prepare the drop statement using select and run it manually if this is one-time thing:
select concat('DROP TABLE IF EXISTS ',table_name) dropstatements
from tables_to_drop
I have a table which has 50+ columns but only few columns are getting used. that means when any stored procedure uses that table it only refers 4-5 columns in select/where statements . rest of columns are not getting used . i just want to list down those columns that are actually getting used. one way is finding out the dependencies of a table and then go through every SP and find out which columns are getting used . but in that case i have around 30+ Sp. is there any efficient way to do it.
To use multiple columns in a procedure, you can use a code like below
create procedure sp_sample
#column_names varchar(200)
as
if #column_names='' or #column_nams is null
set #column_names='*'
exec ('select '+#column_name +' from table')
Here are some examples :
exec sp_sample #columnname='id,name'
or
exec sp_sample #columnname='id,name,telphone'
Try this:
select name from syscomments c
join sysobjects o on c.id = o.id
where TEXT like '%table_name%' and TEXT like '%column_name%'
In table_name give you table name, in column_name give the column for which you want to chck the procedure dependencies.You will get the stored procedure names as output
If you import your database as a database project using the SQL Server Data Tools, you will be able to find all references to a table or column using the "Find All References" context command. What makes this particularly useful is the accuracy: it will even find instances of SELECT * that don't mention the column explicitly, but implicitly refer to it anyway. It will also not be confused by tables or columns with similar names (finding particular instances of ID is otherwise rather problematic).
If all you want to know if a column is referenced at all, you can simply delete it and see if any "unresolved reference" errors appear in the error list -- if yes, then the column is used somewhere.
I have a big table with names and surnames. People search this database via a Web interface. PHP code queries the table with LOWER(#name) = LOWER(name). In order to make the search faster, I want to make a derived column in the table named lower_name and always LOWER() the names before storing. But when it comes to send the results to web interface, I want to show the original ones. However, I don't want to change the table structure. Is there some kind of Index that automatically does the trick or an option to create an "invisible column" in SQL Server or something like that?
You can create a presisted computed column with an index on it:
ALTER TABLE YourTable ADD lower_name AS LOWER(name) PERSISTED
go
CREATE NONCLUSTERED INDEX IX_YourTable_lower_name
ON YourTable (lower_name)
go
You do not INSERT or UPDATE this column, the DB will do it for you and always keep it in sync with your "name" column.
If you don't want to use a computed column you could create a view, that has the LOWER(name) AS lower_name column in it and put an index on that column:
http://msdn.microsoft.com/en-us/library/cc917715.aspx
You have various options:
declare the column Name case-insensitive using the COLLATE clause
compare Name and #Name using the COLLATE clause
create a computed column LowerName AS LOWER(Name) PERSISTED and index this computed column
PHP code queries the table with
LOWER(#name) = LOWER(name)
Thanks in a world of pain. LOWER(name) triggers a table scan. This is not making it faster, it is - brutally - a beginner mistake that kills performance. You should never compare against a calculation of the table fields, unless you ahve the result in a precaculated index (as you can do in SQL Server 2008, for example).
What about
WHERE name LIKE #name
which should ignore case... plus an Index on the name field.
I have a table which has essentially boolean values in a legacy database. The column names are stored as string values in another table so I need to match the column names of one table to a string value in another table. I know there has to be a way to do this directly with SQL in SQL Server but it is beyond me.
My initial thought was to use PIVOT but it is not enabled by default and enabling it would likely be a difficult process with pushing that change to the Production database. I would prefer to use what is enabled by default.
I am considering using COALESCE to translate the boolean value to the string that value that I need. This will be a manual process.
I think I will also use a table variable to insert the results of the first query into that variable and use those results to do the second query. I still have the problem that the columns are on a single row so I wish I could easily pivot the values to put the column names in the result set as strings. But if I could easily do that I could easily write the query with a sub-select.
Any tips are welcome.
Checkout Sysobjects and SysColumns in SQL Server. They are 2 SQL tables that gives you the names of the tables in your DB and the names of the columns that go with that table.
The system view INFORMATION_SCHEMA.COLUMNS will also give you what you want.
You can build a SQL string and then execute that string as a query. Not the prettiest by any means but I think it would work the way you want it to. You would just use a cursor or while loop to build the string.
If you're comfortable with .Net you could just write your own stored proc in your language of choice and manipulate the data in code instead.
Heres a link to get started
CLR Stored Procedures
I'm not quite sure I understand how your design is currently put together (could you post an example?), but the information_schema.columns view will give you a table containing all the column names as string values. If you join your second table against that I think you'll probably get what you need.
For Example, i have a table STATEtbl having 3 columns and i want to get all the column names of this table as ROW values... i use the below query
Select SC.name as Columns from Syscolumns SC
Join Sysobjects SO On SC.id = SO.Id
where Object_name(SO.Id) = 'STATEtbl'
Result of the query:
Columns
--------
State
StateCode
StateFullName
I have a table in informix (Version 11.50.UC4) called NextRecordID with just one column called id and it will have one row. What I want to do is copy this value into another table. But don't want my query to fail if this table does not exist. Something like
if table NextRecordID exists
then insert into sometable values ('NextRecordID', (select id from NextRecordID))
else insert into sometable values ('NextRecordID', 1)
I ended up using the below SQL query. Its not ANSI SQL but works the informix server I am using.
insert into sometable values ('NextRecordID',
select case (select 1 from systables where tabname='nextrecordid')
when 1 then (select nextid from nextrecordid)
else (select 1 from systables where tabname='systables') end
from systables where tabname='systables');
What is happening here is within insert query I get the value to be inserted by using select query. Now that select query is interesting. It uses case statement of Informix. I have written a select query to check if the table nextrecordid exists in systables and return 1 if it exists. If this query returns 1, I query the table nextrecordid for the value or else I wrote a query to return the default value 1. This work for me.
You should be able to do this by checking the systables table.
Thank you for including server version information - it makes answering your question easier.
You've not indicated which language(s) you are using.
Normally, though, you design a program to expect a certain schema (certain tables to be present), and then fail - preferably under control - if those tables are not present. Also, it is not clear whether you would get into problems because of repeated execution of the second INSERT statement. Nor is it clear when the NextRecordID table is updated - presumably, once the value has been used, it must be updated.
You should look at SERIAL (BIGSERIAL) and see whether that is appropriate for you.
You should also look at whether a SEQUENCE would be appropriate to use here - it certainly looks rather like it might be applicable.
As Adam Hughes points out, if you want to check whether the NextRecordID table is present in the database, you would look in the systables table. Be aware, though, that your search will need to be against an all lower-case name (nextrecordid).
Also, MODE ANSI databases complicate life - you have to worry about the table's owner (because there could be multiple tables called nextrecordid in a MODE ANSI database). Most likely, you don't have to worry about that - any more than you are likely to have to worry about delimited identifiers for table "someone"."NextRecordID" (which is a different table from someone.NextRecordID).