How to Update SQL Server Statistics for Big Tables

In my previous article, I have briefly covered database statistics, its importance, and why statistics should be updated. Moreover, I have demonstrated a step by step process to create a SQL Server maintenance plan to update statistics. In this article, the following issues will be explained: 1. How to update statistics using T-SQL Command. 2. How to identify the frequently updated tables using T-SQL and also how to update the statistics of tables with frequently inserted/ updated / deleted data . Read More

Calculate the median by using Transact SQL

The statistical median is the value which separates a dataset into halves – one comprises greater values, and the other comprises lesser ones. For a specified dataset, it can be considered as the “middle” value. For example, in the dataset {1, 3, 3, 4, 5, 6, 7, 8, 9}, the median is 5, which is fourth largest, and fourth smallest number in the dataset.

To calculate the median of any dataset, we first need to arrange all values from the dataset in a specific order. After arranging the data, we must determine the middle value of the specified dataset. If the dataset contains an odd number of values, than the middle value of the entire dataset will be considered as a median. Read More

Auto Create Statistics and Auto Update Statistics

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

Several Ways to Insert Split Delimited Strings in a Column

In this article, I will demonstrate several ways to split the delimited string and insert it in into a column of a table in SQL Server. You can do it using the following methods:

  1. Convert delimited string into XML, use XQuery to split the string, and save it into the table.
  2. Create a user-defined table-valued function to split the string and insert it into the table.
  3. Split the string using STRING_SPLIT function and insert the output into a table. Read More

T-SQL SET Operators Part 2: INTERSECT and EXCEPT

In my previous article, I explained the basics of set operators, their types, and prerequisites for their use. I also talked about UNION and UNION ALL operators, their usage and differences.

In this article, we’re going to learn the following:

  1. EXCEPT and INTERSECT operators.
  2. Difference between INTERSECT and INNER JOIN.
  3. The detailed explanation of INTERSECT and EXCEPT with an example.

EXCEPT and INTERSECT operators were introduced in SQL Server 2005. Both are set operators used to combine the result sets generated by two queries and retrieve the desired output. Read More

How to Properly Use the T-SQL IsNumeric Function

This article is focused on the T-SQL (Transact-SQL) IsNumeric function and its proper use in day-to-day SQL scripting tasks.

We will also see why it is important to understand how and why IsNumeric can be used – both incorrectly and correctly.

There may be some better alternatives to IsNumeric depending on the context. However, in the cases we’re going to cover in this article, I see this function as the best possible choice. Read More

T-SQL Datetime Data Type

Introduction

Data types are attributes that specify the kind of data that objects such as columns, local variables, expressions, and parameters can hold. Across the RDBMS world, data types are typically grouped into string, numeric, and date data types.

T-SQL supports 6 date and time data types namely:

  1. Datetime
  2. Smalldatetime
  3. Date
  4. Time
  5. Datetime2
  6. Datetimeoffset

The first two data types are considered as legacy versions of the newer ones. In this article, we focus on the date data types and, specifically, on the datetime and datetime2 data types available in SQL Server. Table 1 gives details of the various date and time data types available in SQL Server. Read More

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

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)

Read More

Basic and Complex Uses of Not Equal Comparison Operator in T-SQL

This article is focused on the T-SQL Not Equal comparison operator (<>) and its uses in basic to slightly complicated SQL scripting tasks.

The article also highlights the importance of understanding the correct use of Not Equal comparative operator with expressions.

The Not Equal comparative operator is a very common operator used in T-SQL, however, it is important to understand how to use it effectively in different scenarios.

Read More