新しいKindle本を出版しました。 今回のテーマは、SQLの中でも少し分かりにくいけれど、実務ではとても大事な EXISTS句 と SELECT 1 です。 です。 Amazon Kindleで販売中です。 SQLを書いたり読んだりしていると、こんな書き方を見かけることがあります。 SELECT * FROM ...

CREATE TABLE classes ( class_id SERIAL PRIMARY KEY, class_name VARCHAR(50) NOT NULL ); CREATE TABLE students ( student_id SERIAL PRIMARY KEY, student_name VARCHAR(100 ...

This article discusses the “DROP IF EXISTS” statement available in SQL Server 2016 and later versions. “IF EXITS” is the latest optional clause added in the existing DROP statement in SQL Server 2016 ...

The EXISTS condition is an operator whose right operand is a subquery. The result of an EXISTS condition is true if the subquery resolves to at least one row. The result of a NOT EXISTS condition is ...

Though SQL (Structured Query Language) for databases has proved to be indispensable through decades of use, differences among SQL versions can challenge a software developer. For example, Microsoft's ...