如何自学SQL？ - 知乎
SQL是所有数据库查询的语言，sql由于本身结构化的特点，非常容易入手。 针对不同的数据库，如hivesql、mysql、sqlserver、oracle等，sql语法会有所不同，但是总体上大同小异，只是 …
Should I use != or <> for not equal in T-SQL? - Stack Overflow
Yes; Microsoft themselves recommend using <> over != specifically for ANSI compliance, e.g. in Microsoft Press training kit for 70-461 exam, "Querying Microsoft SQL Server", they say "As …
sql是什么，通俗的说，太专业听不懂？ - 知乎
学习SQL有哪些途径和资料呢？ 其实买一本自学一个礼拜就能搞定，不过这里也给大家推荐一些好的学习资源。 目前市场上SQL相关的资料很多，比较火的像《SQL必知必会》、《SQL学习 …
数据分析人员需要掌握sql到什么程度？ - 知乎
熟悉如何优化SQL语句，以期达到最高查询效率，了解事务、锁、索引、约束、视图、元数据等概念，并且学会使用hive sql、spark sql、pymysql等工具； 数据分析人员最好是能达到第三个 …
sql - NOT IN vs NOT EXISTS - Stack Overflow
Which of these queries is the faster? NOT EXISTS: SELECT ProductID, ProductName FROM Northwind..Products p WHERE NOT EXISTS ( SELECT 1 FROM Northwind..[Order Details] …
SQL: IF clause within WHERE clause - Stack Overflow
Sep 18, 2008 · Is it possible to use an IF clause within a WHERE clause in MS SQL? Example: WHERE IF IsNumeric(@OrderNumber) = 1 OrderNumber = @OrderNumber ELSE …
How do I perform an IF...THEN in an SQL SELECT?
Sep 15, 2008 · The CASE statement is the closest to IF in SQL and is supported on all versions of SQL Server. SELECT CAST( CASE WHEN Obsolete = 'N' or InStock = 'Y' THEN 1 ELSE 0 …
通俗易懂的学会：SQL窗口函数 - 知乎
Oct 12, 2025 · 视频《最通俗易懂的学会SQL窗口函数》 SQL从入门到进阶 (视频+社群) 3.聚合函数作为窗口函数 聚和窗口函数和上面提到的专用窗口函数用法完全相同，只需要把聚合函数 …
sql - What is the difference between JOIN and INNER JOIN
per the ANSI SQL 92 specification, they are identical: "3) If a <qualified join> is specified and a <join type> is not specified, then INNER is implicit."
What is the use of the square brackets [] in sql statements?
The Microsoft book for SQL course says "You should use two-part names to refer to tables in SQL Server databases, such as Sales.Customer" so they don't ask to surround namespace with …