AI代码解释 DELIMITER//CREATEDEFINER=`root`@`localhost`FUNCTIONrand_string2(nINT)RETURNSVARCHAR(255)CHARSETutf8mb4COLLATEutf8mb4_general_ci #该函数会返回一个字符串BEGINDECLAREchars_strVARCHAR(100)DEFAULT'abcdefghijklmnopqrstuvwxyzABCDEFJHIJKLMNOPQRSTUVWXYZ';DECLAREreturn_strVARCHAR(255)DEFAULT'';DECLARE...
unique_subquery is just an index lookup function that replaces the subquery completely for better efficiency. unique_subquery是一个索引查找函数,代替子查询提高效率。 index_subquery This join type is similar to unique_subquery. It replaces IN subqueries, but it works for nonunique indexes in subquer...
This type replaces eq_ref for some IN subqueries of the following form: 比eq_ref复杂的地方是使用了in的子查询,而且是子查询是主键或者唯一索引 valueIN(SELECTprimary_keyFROMsingle_tableWHEREsome_expr) unique_subquery is just an index lookup function that replaces the subquery completely for better ...
The refcolumnshows which columnsorconstants are comparedtotheindexnamedinthekeycolumntoselectrowsfromthetable.Ifthe valueisfunc, the value usedisthe resultofsomefunction.Tosee whichfunction,useSHOW WARNINGS following EXPLAINto see the extended EXPLAIN output. Thefunctionmight actually be an operator such...
18. Please explain the rules of golf to me; I want to learn about it. 请解释高乐夫球规则给我听,我想学。 19. By introducing the principle of application design, process design and exception design, the author explain the system function, target and software structure. ...
This type replaces eq_ref for some IN subqueries of the following form: unique_subquery和eq_ref不一样的地方是使用了in的子查询: valueIN(SELECTprimary_keyFROMsingle_tableWHEREsome_expr) unique_subquery is just an index lookup function that replaces the subquery completely for better efficiency. ...
Related:Python slice() Builtin Function Table of contents 1. Quick Examples of Slice Notation 2. What is Slice Notation in Python? 3. Syntax of Slice Notation 3.1 Parameters 4. List Slice Notation 4.1 Example: Slice Notation [start:] ...
The join type.For descriptions of the different types, see EXPLAIN Join Types. --对表所使用的访问方式。 2.1.5 possible_keys Thepossible_keys column indicates which indexes MySQL can choose from use to findthe rows in this table. Note that this column is totally independent of theorder of th...
What are the types and functions of cells found within the stomach? Describe the function of different cell types. Summarize the functions of the stomach. Describe the functions of each cell structure and then its relation with other functions in the cell. Describe the structure and function...
Understand the scope and function of retention policies in Exchange Online. Identify types of data covered under retention policies and those that are not. Explain the process of transitioning from Messaging Records Management (MRM) to modern retention policies. Navigate the retention and ...