`last_update`timestampNOTNULLDEFAULTCURRENT_TIMESTAMPONUPDATECURRENT_TIMESTAMP,PRIMARYKEY(`person_id`),KEY`idx_p_a` (`postadlcode`,`age`),KEY`idx_f_l` (`first_name`,`last_name`) ) ENGINE=InnoDBDEFAULTCHARSET=utf8 关闭ICP优化,Extra信息为“Using Where” mysql>setoptimizer_switch="index_c...
#2. mysql中的primary key,unique,联合唯一也都是索引,这些索引除了加速查找以外,还有约束的功能 2、MySQL常用的索引 普通索引INDEX:加速查找 唯一索引:-主键索引PRIMARYKEY:加速查找+约束(不为空、不能重复)-唯一索引UNIQUE:加速查找+约束(不能重复) 联合索引:-PRIMARYKEY(id,name):联合主键索引-UNIQUE(id,name)...
Growth mechanisms to explain the primary and secondary habits of snow crystals . Phil. Mag. , 81 , 2337 – 2373Nelson, J. 2001 Growth mechanisms to explain the primary and secondary habits of snow crystals. Phil. Mag. A 81, 2337-73....
Explain three different methods for primary data collection. Market Research: Market research is an important step in product development and inadequate research may result in significant issues for a business. Primary data is gathered actively while secondar...
ReplicationReplicates data to secondariesReplicates data from the primary or another secondary ElectionElected node, initiates writesCan be promoted to primary during an election Health CheckCritical for replica set operationCan be down temporarily without affecting writes ...
1.3.2 PRIMARY 对于包含UNION、UNION ALL或者子查询的大查询来说，它是由几个小查询组成的，其中最...
That is, thenamed index covers the selected columns, so although it is not used to determinewhich rows to retrieve, an index scan is more efficient than a data row scan. For InnoDB, a secondary index might coverthe selected columns even if the query also selects the primary key becauseInn...
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The processes of primary and secondary succession in an extremely long period time period? True or false? Explain.Succession:In biology and ecology, succession refers to processes in which plants or other species take on different structures. This can result in ...