5+ Sql Substring 使い方 Article

SQL SUBSTRING Function from www.tutorialgateway.org

Introduction

SQL Substring is a widely used function that extracts a portion of a string. It can be used to manipulate the data in a database table and retrieve specific information. In this article, we'll explore the different ways of using SQL Substring function.

Basic Syntax

The basic syntax of the SQL Substring function is as follows:

SELECT SUBSTRING(string, start_position, length);

The 'string' parameter represents the original string, while the 'start_position' parameter indicates the starting position of the substring. Lastly, the 'length' parameter denotes the number of characters that should be extracted from the string.

Using SQL Substring for Data Manipulation

One of the most common uses of SQL Substring is for data manipulation. Let's say we have a database table with a column called 'Name', which contains the full name of each record. If we only want to retrieve the first name, we can use SQL Substring to extract it.

SELECT SUBSTRING(Name, 1, CHARINDEX(' ', Name) - 1) AS FirstName FROM TableName;

This query will return the first name of each record in the 'Name' column.

Using SQL Substring for Data Validation

Another use of SQL Substring is for data validation. Let's say we have a column called 'Phone' that contains phone numbers in different formats. We want to ensure that all phone numbers are in the same format. We can use SQL Substring to extract the area code and phone number separately.

SELECT SUBSTRING(Phone, CHARINDEX('(', Phone) + 1, 3) AS AreaCode, SUBSTRING(Phone, CHARINDEX(')', Phone) + 2, 8) AS PhoneNumber FROM TableName;

This query will return the area code and phone number separately for all records in the 'Phone' column.

Using SQL Substring for Data Analysis

SQL Substring can also be used for data analysis. Let's say we have a column called 'Date' that contains dates in the format 'YYYY-MM-DD'. We want to retrieve the year and month separately for analysis purposes.

SELECT SUBSTRING(Date, 1, 4) AS Year, SUBSTRING(Date, 6, 2) AS Month FROM TableName;

This query will return the year and month separately for all records in the 'Date' column.

Conclusion

In conclusion, the SQL Substring function is a powerful tool for data manipulation, validation, and analysis. It can be used in a variety of ways to extract specific information from a string. By understanding the basic syntax and different use cases, you can improve your SQL skills and make more informed data-driven decisions.