Fetching the data from different databases

Question

Can anyone explain getting data joining different databases with sql query script

Tuhin Paul · Answer

SQL Query for Data Integration The query below demonstrates how to join these databases. It assumes that linked servers or federated tables have been set up to allow cross-database querying. -- This query retrieves active policies along with associated customer, vehicle, and claim details SELECT c.CustomerID, c.Name AS CustomerName, c.Email AS CustomerEmail, p.PolicyID, p.PremiumAmount, p.StartDate, p.EndDate, v.VIN, v.Make, v.Model, v.Year, cl.ClaimID, cl.ClaimStatus, cl.ClaimAmount, cl.ClaimDate FROM CustomerDB.dbo.Customers AS c JOIN PolicyDB.dbo.Policies AS p ON c.CustomerID = p.CustomerID JOIN VehicleDB.dbo.Vehicles AS v ON p.VehicleID = v.VehicleID LEFT JOIN ClaimsDB.dbo.Claims AS cl ON p.PolicyID = cl.PolicyID WHERE p.EndDate >= GETDATE() -- Filter to include only active policies ORDER BY c.CustomerID, p.PolicyID;

Tuhin Paul · Answer

Part -1

Muhammad Imran Ansari · Answer

Joining data from different databases using SQL is a common task, especially when working with distributed systems or multiple data sources. The exact method depends on the database management system (DBMS) you're using (e.g., MySQL, PostgreSQL, SQL Server, etc.), but the general concept is similar across systems. Points to remember: Fully Qualified Table Names: To access tables in different databases, you need to use fully qualified table names, which typically include: Database name, Schema name and Table name. Cross-Database Queries: Most DBMSs allow you to query tables from different databases as long as you have the necessary permissions and the databases are on the same server. Linked Servers or Database Links: For databases on different servers, you may need to set up linked servers (SQL Server) or database links (Oracle). General Tips: Permissions: Ensure you have the necessary permissions to access the databases and tables. Performance: Cross-database queries can be slower, especially if the databases are on different servers. Optimize your queries and consider indexing common columns. Data Consistency: Be mindful of data consistency when joining tables from different databases, especially if they are updated independently.

Tharunkumar Magudeeswaran · Answer

You can fetch data from different databases using fully qualified table names or cross-database queries (if supported). Example (SQL Server): SELECT a.Emp_ID, a.Emp_Name, b.Salary FROM DatabaseA.dbo.Employee a JOIN DatabaseB.dbo.SalaryDetails b ON a.Emp_ID = b.Emp_ID; Ensure you have the necessary permissions and that the databases reside on the same server . If they are on different servers, consider linked servers or ETL approaches like ADF.

Fetching the data from different databases

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