Use Cases for SQL Server MERGE Statement: Syncing Online and History Tables

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INTRODUCTION

The SQL Server MERGE statement is an incredibly useful tool for carrying out DML operations based on comparing two tables or two data sets. Usage of this statement is actually like performing multiple operations in a single statement.

This article will explore three use cases that border on ensuring data between an online table and a history table in sync.

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Your Ultimate Guide to SQL Join: CROSS JOIN – Part 3

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CROSS JOIN is in the spotlight. This article finishes our small series of SQL JOIN-related publications. If you missed the previous two articles, refer to them as follows:  

SQL Server CROSS JOIN is the simplest of all joins. It implements a combination of 2 tables without a join condition. If you have 5 rows in one table and 3 rows in another, you get 15 combinations. Another definition is a Cartesian Product.

Now, why would you want to combine tables without a join condition? Hang on a bit because we are getting there. First, let’s refer to the syntax.

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Add Columns to an Existing Table in SQL Server Database

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Introduction

A table is a two-dimensional logical structure and the fundamental means of storing data in relational database management systems. Its ‘row and column’ format is very much like the organization of the spreadsheet. 

Each new record introduced to a table is a row (also called a record or tuple), while rows are grouped into a finite set of columns (also called fields or attributes). Each column has a name and data type, and it serves as a reference for displaying result sets when querying data from relational database systems.

In this article, we explore the current options letting us add new columns to an existing table in SQL Server database. The use case may arise on many occasions. Particularly, it happens when there are updates for an application, and they demand adding new columns.

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Your Ultimate Guide to SQL Joins: OUTER JOIN – Part 2

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Outer join is at the center stage today. And this is part 2 of your ultimate guide to SQL joins. If you missed part 1, here’s the link.

By the looks of it, outer is the opposite of inner. However, if you consider the outer join this way, you’ll be confused. To top that, you don’t have to include the word outer in your syntax explicitly. It’s optional!

But before we dive in, let’s discuss nulls concerning outer joins.

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The Easy Guide on How to Use Subqueries in SQL Server

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Do you use SQL subqueries or avoid using them?

Let’s say the chief credit and collections officer asks you to list down the names of people, their unpaid balances per month, and the current running balance and wants you to import this data array into Excel. The purpose is to analyze the data and come up with an offer making payments lighter to mitigate the effects of the COVID19 pandemic.

Do you opt to use a query and a nested subquery or a join? What decision will you make?

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Auto Create Statistics and Auto Update Statistics

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Statistics comprises lightweight objects that are used by SQL Server Query optimizer to determine the optimal way to retrieve data from the table. SQL Server optimizer uses the histogram of column statistics to choose the optimal query execution plan. If a query uses a predicate which already has statistics, the query optimizer can get all the required information from the statistics to determine the optimal way to execute the query. SQL Server creates statistics in two ways:

  1. When a new index is created on a column.
  2. If the AUTO_CREATE_STATISTICS option is enabled.

In this article, Auto Create Statistics and Auto Update Statistics options are analyzed. They are database specific and can be configured using SQL Server management studio and T-SQL Query. Read More

Advanced SQL: Variations and Different Use cases of T-SQL Insert Statement

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In my previous article, I demonstrated:

  1. Insert the output of the table-valued function in the SQL table.
  2. Insert the output of the table-valued function that is created on the remote database server.

In this article, I am going to demonstrate:

  1. Copy data between two tables, created in a different schema.
  2. Copy data between two tables, created in different databases on the same server.
  3. Copy data between two tables created, in different databases resides the different server (Cross server query)

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SQL Server Bulk Insert – Part 2

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In the previous part of this article, we discussed how to import CSV files to SQL Server with the help of BULK INSERT statement. We discussed the main methodology of bulk insert process and also the details of BATCHSIZE and MAXERRORS options in scenarios.  In this part, we will go through some other options (FIRE_TRIGGERS, CHECK_CONSTRAINTS and TABLOCK) of bulk insert process in various scenarios.

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