range can be used when a key column is compared to a constant using any of the =, <>, >, >=, <, <=, IS NULL, <=>, BETWEEN, or IN() operators: # 常量比较,可能多行(但是这里的例子和上面ref的第一个例子不一样吗?)SELECT*FROMtbl_nameWH
使用索引检查指定范围的行时。 range can be used when a key column is compared to a constant using any of the =, <>, >, >=, <, <=, IS NULL, <=>, BETWEEN, LIKE, or IN() operators: index# index和ALL类似,但index出现在索引被扫描了的情况下,有两种情况: 如果索引是查询的一个覆盖索...
it displays the execution plan for the statement executing in the named connection. See Section 8.8.4, “Obtaining Execution Plan Information for a Named Connection”. 当EXPLAIN与FOR CONNECTION connection_id而不是可解释语句一起使用时,它将显示在指定连接中执行的语句的执行计划。参见...
range can be used when a key column is compared to a constant using any of the =, <>, >, >=, <, <=, IS NULL, <=>, BETWEEN, LIKE, or IN() operators: 通过索引范围查找多行数据,可以使用=, <>, >, >=, <, <=, IS NULL, <=>, BETWEEN, LIKE, 或 IN() 操作符。 //多行...
The order of the operators and their implementations is decided by the query optimizer using a combination of query transformations and physical optimization techniques. While the display is commonly shown in a tabular format, the plan is in fact tree-shaped. For example, consider the following ...
By default,DESCRIBEdisplays information about all columns in the table.col_name, if given, is the name of a column in the table. In this case, the statement displays information only for the named column.wild, if given, is a pattern string. It can contain the SQL%and_wildcard characters...
Range can beused when a key column is compared to a constant using any of the =, <>, >, >=, <, <=, IS NULL, <=>, BETWEEN, or IN() operators: index 这种连接类型和all一样,除了扫描索引树。发生在下面两种情况: 1、如果对于查询索引是一个覆盖索引并且可以满足这个表所有数据的查询,只是...
Similarly in a C++ program all the C++ statements having Keywords, Identifiers, Constants, Strings, Operators and the Special Symbols are called C++ Tokens. C++ Tokens are the essential part of a C++ compiler and so are very useful in the C++ programming. A Toke...
range can be used when a key column is compared to a constant using any of the =, <>, >, >=, <, <=, IS NULL, <=>, BETWEEN, LIKE, or IN() operators: SELECT * FROM tbl_name WHERE key_column = 10; SELECT * FROM tbl_name WHERE key_column BETWEEN 10 and 20; SELECT * ...
Action: Re-phrase the query to avoid the use of set operators. QSM-02022 aggregate selections Cause: The capability in question is not supported when the materialized view uses an aggregate expression in the HAVING clause. Action: Re-phrase the query to avoid the use of an aggregate in the...