I have MS Access tables that are indexed but accept duplicates. Tables have been transferred to SQL Server and linked to Access.
How do you replicate primary keys that accept duplicates?
You should consider using SSMA
Sql Server Migration Assistant for Access
It can move up tables.
It will move up related data, setup PK columns for you.
It will maintain, and create relationships for you.
It will maintain and create all indexes you have now.
If you just have a few tables, say 2-5 tables? Then sure, just import them and setup the relatonships and indexs your self.
However, the last few migrations of data from Access to SQL server? There was in excess of 80 tables - and HUGE numbers of reatonships, indexes, and of course PK settings. The migration wizard thus can send up all of the tables - and setup all of the tables correctly on SQL server for you. Including PK values, FK values (Foreign Keys (related tables)),
and even constraints are in most cases correctly move up to sql server.
what is nice, is then you can re-link the tables in your Access application, and you now using SQL server for the back end database.
SSMAA can be found here:
https://www.microsoft.com/en-us/download/details.aspx?id=54255
I think you're confusing an "index" with a "primary key".
An "index" is a structure that helps optimise queries. Indexes don't have to be unique. A "primary key" is a logical constraint on a column which requires that all values in the column are unique.
It sounds like what you want to do is import the data into SQL and create an index to help speed up queries, but where that index is not constrained to be unique.
Here's the syntax to do that. Suppose we have some table T:
create table T(i int, j int, k int);
We want to create an index on column i to speed up queries, but i is not unique. To do that we create a regular (non unique) index:
create index MyIndexName on T(i);
As a rule, I tend to name my indexes based on what they are indexing. So in the above case I wouldn't call the index "MyIndexName", I would call it something like ix_T_i.
Related
Very new to sql server. I have a db with about 20 tables each with around 40 columns. How can I select two tables and see if they have any columns in common?
I basically want to see where I can make joins.. If there's a better way of quickly telling where I can combine info from two tables that could be helpful too.
First of all, in relational databases there is not such a concept of "joinable tables and/or columns". You can always list two relations (= tables) crossing every row in one relation with each row of the other (the cross/carthesian product of them) and then filter those based on some predicate (also called a "join", if the predicate involves columns of both relations).
The idea of "joinable" tables/columns comes into being only when thinking about the database schema. The schema's author can ask the database engine to enforce some referential integrity, by means of foreign keys.
Now if your database schema is well done (that is, its author was kind/clever enough to put referential integrity all over the schema) you can have a clue of which tables are joinable (by which columns).
To find those foreign keys, for each table you can run sp_help 'databasename.tablename' (you can omit the databasename. part, if it is the current database).
This command will output some facts about the given table, like its columns (along with their datatypes, requiredness, ...), its indexes and so on. Somewhere near the end it will list foreign keys along with where (if ever) its primary key is imported as foreign key on other tables.
For each key imported as foreign key on other table you have a candidate predicate for a join.
Please note that this procedure will only work if the foreign keys are set correctly. If they aren't, you can fix your database schema (but to do this you must know already which tables are joinable anyway). Also it won't show you joinable tables on other databases (in the same or linked server).
This also won't work for views.
Try to see in the SQL Management Studio, in the database diagram, there you find the relations between tables.
Is there a way in SQL Server to create an index with data that doesn't exist in the table itself? for example, create an index that points to the primary key, but where each row also includes custom data that the DBA inserts into the index, where this data does not really exist in the columns themselves.
Not sure what you're trying to do but it seems like you're thinking a bit more physical implementation than logical design. What you describe is a related table, not an index. Indexes may be used to make it work/enforce integrity with a reasonable performance but they are not storage mechanisms in the first instance (covering indexes aside).
My company has an application with a bunch of database tables that used to use a sequence table to determine the next value to use. Recently, we switched this to using an identity property. The problem is that in order to upgrade a client to the latest version of the software, we have to change about 150 tables to identity. To do this manually, you can right click on a table, choose design, change (Is Identity) to "Yes" and then save the table. From what I understand, in the background, SQL Server exports this to a temporary table, drops the table and then copies everything back into the new table. Clients may have their own unique indexes and possibly other things specific to the client, so making a generic script isn't really an option.
It would be really awesome if there was a stored procedure for scripting this task rather than doing it in the GUI (which takes FOREVER). We made a macro that can go through and do this, but even then, it takes a long time to run and is error prone. Something like: exec sp_change_to_identity 'table_name', 'column name'
Does something like this exist? If not, how would you handle this situation?
Update: This is SQL Server 2008 R2.
This is what SSMS seems to do:
Obtain and Drop all the foreign keys pointing to the original table.
Obtain the Indexes, Triggers, Foreign Keys and Statistics of the original table.
Create a temp_table with the same schema as the original table, with the Identity field.
Insert into temp_table all the rows from the original table (Identity_Insert On).
Drop the original table (this will drop its indexes, triggers, foreign keys and statistics)
Rename temp_table to the original table name
Recreate the foreign keys obtained in (1)
Recreate the objects obtained in (2)
I have a question related to database design. The database that I'm working with
requires data to treated in some way that it is never physically deleted. We started going
down a path of adding a "DeleteDateTime" column to some tables, that is NULL by default but
once stamped would mark a record as deleted.
This gives us the ability archive our data easily but I still feel in the dark on a few areas, specifically
whether this would be considered in line with best practices and also how to go about indexing these tables efficiently.
I'll give you an example: We have a table called "Courses" with a composite primary key made up of the columns "SiteID" and "CourseID".
This table also has a column called "DeleteDateTime" that is used in accordance with my description above.
I can't use the SQL Server 2008 filtered view feature because we have to be
SQL Server 2005 compatible. Should I include "DeleteDateTime" in the clustered index for this table? If so should it be
the first column in the index (i.e. "DeleteDateTime, SiteID, CourseID")...
Does anyone have any reasons why I should or shouldn't follow this approach?
Thanks!
Is there a chance you could transfer those "dead" records into a separate table? E.g. for your Courses table, have a Courses_deleted table or something like that, with an identical structure.
When you "delete" a record, you basically just move it to the "dead table". That way, the index on your actual, current data stays small and zippy....
If you need to have an aggregate view, you can always define a Courses_View which unions the two tables together.
Your clustered index on your real table should be as small, static and constant and possible, so I would definitely NOT recommend putting such a date time column into it. Not a good idea.
For excellent info on how to choose a good clustering key, and what it takes, check out Kimberly Tripp's blog entries:
GUIDs as PRIMARY KEYs and/or the clustering key
The Clustered Index Debate Continues...
Ever-increasing clustering key - the Clustered Index Debate..........again!
Marc
what's your requirements on data retention? have you looked into an audit log instead of keeping all non-current data in the database?
I think you have it right on the head for the composite indexes including your "DeleteDateTime" column.
I would create a view that is basically
select {List all columns except the delete flag}
from mytable
where deletflag is null
This is what I would use for all my queries on the table. The reason why is to prevent people from forgetting to consider the deleted flag. SQL Server 2005 can easily handle this kind of view and it is necessary if you are goin to use thisdesign for delting records. I would have a separate index on the delted column. I likely would not make it part of the clustered index.
I am using SQL Server 2000 and I have two databases that both replicate (transactional push subscription) to a single database. I need to know which database the records came from.
So I want to add a fixed column specified in the publication to my table so I can tell which database the row originated from.
How do I go about doing this?
I would like to avoid altering the main databases mostly due to the fact there are many tables I would need to do this to. I was hoping for some built in feature of replication that would do this for me some where. Other than that I would go with the view idea.
You could use a calculated column Use the following on the two databases:
ALTER TABLE TableName ADD
MyColumn AS 'Server1'
Then just define the single "master" database to use a VARCHAR column (or whatever you want) that you fill using the calculated columns value.
You can create a view, which adds the "constant" column, and use it as a replication source.
So the solution for me was to set up the replication publications to allow transformations and create a DTS package for each site that appends the siteid into the tables to keep the ids unique as I can't use guids.