Databases are at the heart of most modern web applications, and PostgreSQL is one of the most popular relational database systems out there. One powerful feature of PostgreSQL—and SQL in general—is the CASE expression. It brings an element of conditional logic to the world of querying, allow...
Erweitern Sie Ihre bedingten Abfragen in PostgreSQL mit CASE-Anweisungen und bedingten Ausdrücken. Folge den Beispielen mit WHEN-THEN, if-else und switch noch heute!
SQL:搞懂case语句,看这篇就可以啦! SQL里CASE 语句允许数分同学在查询中执行条件逻辑。了解如何使用其功能可以显著增强工作效率和数据处理的能力。在本文中,我们将深入探讨 SQL CASE 语句,涵盖其语法、各种用例,并提供实用的代码示例来巩固大家的理解。 Part1-了解 SQL CASE 语句 CASE 语句提供了在 SQL 查询中执行...
importpsycopg2importpandasaspdfromsqlalchemyimportcreate_engine,text# 连接数据库取数engine=create_engine('postgresql+psycopg2://postgres:123456@127.0.0.1:5432/sql_advanced')df=pd.read_sql_query('SELECT * FROM poptbl',engine)# 创建一个字典,用来映射pref_name和districtdistrict_map={'德岛':'九州','...
在PostgreSQL中有一个函数可以直接得出结果: select key_name, GREATEST(x, y, z) AS maximum_value FROM greatests; 那么如果不使用自带的函数方法,该怎么是现在这个需求呢?我们使用两两比较的方式进行判断,我们可以写出这样的语句: select key_name, CASE WHEN x >= y AND x >= z THEN x WHEN y >=...
statement to create or formulate a query/expression. It can be used with any statement or clause where an expression can be used, such as with a WHERE clause, with the SELECT statement, etc. This post has presented various examples to explain the usage of the case statement in PostgreSQL....
Summary: in this tutorial, you will learn how to use the PostgreSQL CASE conditional expression to form conditional queries. The PostgreSQL CASE expression is the same as IF/ELSE statement in other programming languages. It allows you to add if-else logic to the query to form a powerful query...
by Baji Shaik and Scott Mead on 11 AUG 2023 in Advanced (300), Amazon Aurora, Amazon RDS, PostgreSQL compatible, RDS for PostgreSQL Permalink Comments Share It’s important to be aware of the case sensitivity of text data in PostgreSQL when performing queries or comparisons to ensure that ...
Under such circumstances, there comes the need forcase-insensitivequeries. The case-insensitive queries will return the search results without bothering about the case. Let’s see how can we query the case-insensitive queries in PostgreSQL.
When you insert some records, notice that PostgreSQL will accept “duplicated terms”. INSERTINTOusers(name,username)VALUES('John Doe','john');INSERTINTOusers(name,username)VALUES('Doe, John','JOHN'); If you select all records with a query likeSELECT * FROM usersyou can see that you have...