I have two tables with identical column names and types, I would like to query all of the content from both tables into one result set, of just one set of column names. So tbl1.ID and tbl2.ID should be in one col.ID as tbl1.data and tbl2.data should be in one col.data. There are no common values between the tables, records are unrelated so nothing to JOIN on.
I am using vb.net to query an Access DB and update a SQL DB.
I believe in SQL I can use a SELECT INTO but I am not sure how to do this in access with one query, or do I need to create a table and just push everything into it first.
thanks,
In Access you can create a "Union Query". How this is done exactly depends on the version of Access you are using. Open that query in "SQL View" and then use the code from there in your VB application.
Related
I´m quite new to the Oracle SQL Developer. I try to handle a big database and I need to define views. Therefore, I need the relationships of some tables. with the relational models of the Browser, I´m able to show ALL relationships of the table, which is quite confusing.
Is there a way to show the ralationships of just one column?
I want to pick the table and the column and I want to see to which other tables the column is connected.
Thank you.
My suggestion:
First find out in which tables the column name has been used :
select * from all_tab_columns where column_name='COLUMN_NAME';
And then you can see constraints defined for the respective columns in that tables
I have a clickhouse database. It contains multiple databases. The tables inside the databases are identical.
For example DB1 has the table "Table1", DB2 also has the table "Table1" (Here the databases are different, Tables are also different but they have identical schema and contain similar type of information).
Is there a way that i can write a query to get the information from all the different tables from all the different databases optimally? Currently i am querying each table individually and doing an Union among them.
You could set up a special table with Merge engine (not to be confused with MergeTree). Querying it will do the the same UNION ALL transparently. It does not support spanning through multiple databases though, so you still might end up having multiple of those or moving the tables into one db.
I would propose to create one more DB:
create database <your_db_name> on cluster <your_cluster_name>;
Then create a Merge table for each of you existing DB:
CREATE TABLE <your_db_name>.<merge_table_name> On cluster <your_cluster_name> (<fields list you need to deal with>) ENGINE=Merge(<existing_db_name>, '<regex>');
Create a View for each of the Merge tables (using a view you can execute any aggregate functions, group by and etc.):
CREATE VIEW <your_db_name>.view_<merge_table_name> on cluster <your_cluster_name> (<list of fields>) AS SELECT <list of fields> FROM <your_db_name>.<merge_table_name>;
Finally create a "result" Merge table that combines all the views newly created:
CREATE TABLE <your_db_name>.<result_table_name> on cluster <your_cluster_name> (<list of fields>) ENGINE=Merge(<your_db_name>, '<regex>');
Name the tables and views in such a way that your regular expression matches all you need and make sure you avoid loops.
I am working on a project, where a user will select a a table choice on a website. Once the table is selected, the website will then connect to the database and select the table from a server (Server A) under a database (ABC). The website will also have to choose the same table from a different server (Server B) under database (DEF). Also these tables will have the same name, they will have some different data entered into them.
Our goal is to come up with a dynamic SQL Query/Stored Procedure. Multiple table choices can be visible in the website and once the user picks an option, it DYNAMICALLY passes that information to the database to find the two tables and yield a final table that portrays the differences.
MY PROBLEM:
I am having a lot of problem with the syntax and doing this process dynamically. I have searched everywhere for a solution and am struggling with this for more than two weeks.
OUTLINE OF MY PLAN:
Find primary keys and the column names of all the columns in a selected table. Pass this information to a temporary table
Create a SQL query with something like :
SET #SQL = select table1.col1, table2.col1... inner join..
Take care of conditions where :
A. Data is present in one table but not the other
B. Data is present in both tables
C. What if there is no data in one or both tables.
I would really appreciate any help. I am very new to SQL and have been trying my hardest in this project for a while. Please help me and I will do my best to repay you. Thank you very much for your time.
This is a bit complex query which has multiple joins and reruns a lot of records with several data fields. Let’s say it basically use to retrieve manager details.
First set of tables (already implemented query):
Select m.name, d.name, d.address, m.salary , m.age,……
From manager m,department d,…..etc
JOINS …..
Assume, a one manger can have zero or more employees.
Let’s say I need to list down all employee names for each and every manager for result of first set of tables with managers who has no employees (which means want to keep the manager list of first set of tables as it is).
Then I have to access “employee” table through “party” tables (might be involved few more tables).
Second set of tables (to be newly connected):
That means there are one or more join with “employee” , “party” and …..etc
I have two approaches on this.
Make left outer join with first set of tables to second set of
tables.
Create a user define function (UDF) in DB level for second set of
tables. Then I have to insert manger id in to this UDF as a
parameter and take all the employees (e1,e2,…) as a formatted string
by calling through the select clause in the first set of tables
Please can someone suggest me the best solution in DB performance wise out of these two options?
Go for the JOIN, using appropriate WHERE clauses and indexes.
The database engine is far better at optimizing that you'll ever be. Let it do its job.
Your way sounds like (n+1) query death.
Write a sample query and ask your database to EXPLAIN PLAN to see what the cost is. If you spot a TABLE
Huge database in mssql2005 with big codebase depending on the structure of this database.
I have about 10 similar tables they all contain either the file name or the full path to the file. The full path is always dependent on the item id so it doesn't make sense to store it in the database. Getting useful data out of these tables goes a little like this:
SELECT a.item_id
, a.filename
FROM (
SELECT id_item AS item_id
, path AS filename
FROM xMedia
UNION ALL
-- media_path has a different collation
SELECT item_id AS item_id
, (media_path COLLATE SQL_Latin1_General_CP1_CI_AS) AS filename
FROM yMedia
UNION ALL
-- fullPath contains more than just the filename
SELECT itemId AS item_id
, RIGHT(fullPath, CHARINDEX('/', REVERSE(fullPath))-1) AS filename
FROM zMedia
-- real database has over 10 of these tables
) a
I'd like to create a single view of all these tables so that new code using this data-disaster doesn't need to know about all the different media tables. I'd also like use this view for insert and update statements. Obviously old code would still rely on the tables to be up to date.
After reading the msdn page about creating views in mssql2005 I don't think a view with SCHEMABINDING would be enough.
How would I create such an updateable view?
Is this the right way to go?
Scroll down on the page you linked and you'll see a paragraph about updatable views. You can not update a view based on unions, amongst other limitations. The logic behind this is probably simple, how should Sql Server decide on what source table/view should receive the update/insert?
You can modify partitioned views, provided they satisfy certain conditions.
These conditions include having a partitioning column as a part of the primary key on each table, and having a set on non-overlapping check constraints for the partitioning column.
This seems to be not your case.
In your case, you may do either of the following:
Recreate you tables as views (with computed columns) for your legacy soft to work, and refer to the whole table from the new soft
Use INSTEAD OF triggers to update the tables.
If a view is based on multiple base tables, UPDATE statement on the view may or may not work depending on the UPDATE statement. If the UPDATE statement affects multiple base tables, SQL server throws an error. Whereas, if the UPDATE affects only one base table in the view then the UPDATE will work (Not correctly always). The insert and delete statements will always fail.
INSTEAD OF Triggers, are used to correctly UPDATE, INSERT and DELETE from a view that is based on multiple base tables. The following links has examples along with a video tutorial on the same.
INSTEAD OF INSERT Trigger
INSTEAD OF UPDATE Trigger
INSTEAD OF DELETE Trigger