代码语言:javascript 代码运行次数:0 运行 AI代码解释 SELECT*FROMref_tableWHEREkey_column=exprORkey_columnISNULL; index_merge This join type indicates that the Index Merge optimization is used. In this case, the key column in the output row contains a list of indexes used, and key_len contains...
9 index_subquery:和unique_subquery类似,只是子查询使用的是非唯一索引 代码语言:javascript 代码运行次数:0 运行 AI代码解释 valueIN(SELECTkey_columnFROMsingle_tableWHEREsome_expr) 10 range:范围扫描,表示检索了指定范围的行,主要用于有限制的索引扫描。比较常见的范围扫描是带有BETWEEN子句或WHERE子句里有>、>=、...
This series of articles was written by me in 20 years. This module statement is also the last lesson of this series. There was a one-year interval in the middle because of the schedule. At that time, I promised everyone to add it, and now I will pay the debt. In the middle time,...
Mouse events in JavaScript are events triggered by user interactions with a web page using a mouse. There are several types of mouse events, and you can use them to capture user actions like clicks, movements, and more. Here are some common mouse events in JavaScript....
表示临时表使用Duplicate Weedout策略,详见https://mariadb.com/kb/en/duplicateweedout-strategy/,翻译javascript:void(0) unique row not found 对于形如 SELECT … FROM tbl_name 的查询,但没有行能够满足唯一索引或主键查询的条件。 Using filesort
In the realm of software development, handling null and undefined values efficiently is crucial to ensuring the robustness and reliability of applications. TypeScript, a statically typed superset of JavaScript, offers developers a comprehensive suite of tools and techniques for managing null values ...
// Operators have both a precedence (order of importance, like * before +) // and an associativity (order of evaluation, like left-to-right) // A table of operators can be found here // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence) //...
The fragment is not sent to the web server; instead, the browser waits for the web server to return a decode.html resource, and then JavaScript on the web page decodes the fragment into a physical query plan diagram. The query plan is, therefore, not logged by a server external to the...
A lot of programming languages use that mix of parentheses and curly brackets ({and}) to write functions. But many don’t care how you space things out. InJavaScript, and many other languages, I could write the above function a bunch of different ways: ...
Accessibility Object Model:The Accessibility Object Model (or called AOM), an experimental JavaScript API that allows developers to modify the browser accessibility tree, has four phases, and supports for phase one recently landed in Chrome Canary behind the flag. ...