Sql relationship between tables in different databases

How to Document Cross-Database Table Relationships

sql relationship between tables in different databases

Database migration; Regular synchronization between information systems; Importing data from one . The tables are in two different databases on same SQL Server. but there are also defined relations between tables. Looking for some Database Guru's to help me out. Using SQL Server Enterprise is it possible to have a relationship between tables in two different DBs ?. Instead, you store order and customer data in two related tables and then Database relationships are very similar in that they're associations between tables. field (such as AutoNumber in Access of Identity in SQL Server).

All tools support mapping column and table names. Data download is optimized. If the data volume is large, only checksums are downloaded. This optimization is helpful in most cases, but time requirements for performing operations increase with the volume of data.

sql relationship between tables in different databases

In the next step, there is a SQL script with generated migrations. This script can be saved or run directly. To be safe, we can even make a database backup before running this script.

ApexSQL Data Diff tool can create an executable program which runs the script on a selected database.

Performing a Join Between Tables in Different Databases - MySQL Cookbook, 2nd Edition [Book]

This script contains data which needs to be changed, not the logic how to change it. This means that the script cannot be run automatically to provide a recurring import. That is the biggest disadvantage of this approach. You have the ability to visually check differences between databases before synchronization.

Performance decreases when transferring enormous volumes of data. Generated SQL script contains only differences, and thus cannot be reused for automatically synchronizing future data. Below you can see the typical UI of these tools. The only difference compared to the previous method is that there is no data comparison, and the generated SQL script does not contain data differences, but synchronization logic.

The generated script can be easily saved into a stored procedure, and can be run periodically e.

sql server - SQL join between two tables in different databases - Server Fault

This method is useful for automatic imports between databases. The performance of this method is much better than the data compare method. SQL Database Studio provides a similar interface to the data compare method. We need to select the source and target databases or tables.

sql relationship between tables in different databases

Then we need to set up options sync keys, pairing and mapping. There is a graphical query builder feature for setting up all parameters.

sql relationship between tables in different databases

Advantages Advanced knowledge of SQL is not required. This division is often artificial and there are no strict logical boundaries between data assets. There are various reasons for creating such data silos: But data in most environments, from business and logical perspective constitutes one continuous landscape, tables are related to one another and there are no strict boundaries.

How to Document Cross-Database Table Relationships

Why is that a problem? Not being able to define foreign key constraints FKs across databases brings a few problems: Data integrity FKs ensure data referential integrity handled by the database server. Without them it has to be ensured in higher levels and that is not as reliable. Understanding data model Without FKs developers have a hard time understanding and discovering data models and this means problems and costs for reporting, data warehousing or big data projects.

Let's document it There is one thing at least you can do about this - document those relationships. Let's use a great tool for this - Dataedo.

Relational databases: Defining relationships between database tables

It enables you to describe schema of various databases in one repository and define non-existent foreign keys. Install First, we need to download and install Dataedo tool: You will need SQL Server instance for this.

sql relationship between tables in different databases

Create repository and connect to it. Import database schemas Now you need to connect to your databases the ones you want to document and import schema. Just click Add documentation button, provide connection details and Dataedo will read tables, columns, foreign keys etc. In my example I have imported following databases: You can see that Dataedo reads foreign keys and shows you existing table relationships: Define relationships OK, let's now get to documenting those cross-database relationships.

Once all required databases and tables are imported we can create new relationship from table in one database to the table in another database. In our case, we have a time tracking database that has RES table that holds resources.