Скачать или смотреть How to Select Records from the Previous Half Year in MySQL

Learn how to accurately select records from the previous half year in MySQL with simple and effective SQL queries. This guide explains the necessary steps to achieve your goals.
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How to Select Records from the Previous Half Year in MySQL

When working with databases, it’s not uncommon to need data from specific time periods. One such scenario is selecting records from the previous half year in MySQL. If you've encountered a situation where you need to determine the first and last days of the prior half-year, you are not alone. This guide aims to provide a clear method to achieve this by breaking down the solution into manageable parts.

Understanding the Problem

Imagine today is September 9, 2020. You want to obtain the first day (January 1, 2020) and the last day (June 30, 2020) of the previous half-year. While calculating these dates for a quarter might be straightforward, figuring it out for a half-year can be a bit challenging.

Example Scenario

Current Date: 2020-09-09

First Day of Previous Half-Year: 2020-01-01

Last Day of Previous Half-Year: 2020-06-30

To calculate these dates effectively, let's lean on some SQL queries.

The Solution

Rather than using the complicated MAKEDATE function in MySQL, which can become a hassle, there’s a simpler alternative using conditional expressions that we can break down into two parts: finding the first day and last day of the previous half-year.

1. Query for First Day of Previous Half-Year

To find the first day of the previous half-year, you can use the following query:

[[See Video to Reveal this Text or Code Snippet]]

Explanation:

The IF statement checks whether the current month is greater than June.

If it is, it uses the current year to concatenate with -01-01.

Otherwise, it subtracts one from the current year and concatenates with -07-01.

2. Query for Last Day of Previous Half-Year

Next, to find the last day of the previous half-year, you can execute this query:

[[See Video to Reveal this Text or Code Snippet]]

Explanation:

Similar to the previous query, it checks the current month.

If the current month is greater than June, it returns June 30 of the current year.

If not, it returns December 31 of the previous year.

Conclusion

With these straightforward queries, you can easily retrieve records from the previous half-year in MySQL. This method avoids complications and streamlines the process, making it accessible even for those relatively new to SQL. Remember, depending on your current month, these queries will yield the correct first and last days of the previous half-year.

Now you have the tools to efficiently retrieve your data spanning from January to June or from July to December, depending on the time of the year. Happy querying!