MySQL: ON DUPLICATE KEY UPDATE 用法
使用该语法可在插入记录的时候先判断记录是否存在，如果不存在则插入，否则更新，很方便，无需执行两条SQL 无 INSERT INTO osc_visit_stats(stat_date,type,id,view_count) VALUES (?,?,?,?) ON DUPLICATE KEY UPDATE view_count=view_count+?-- osc_visit_st
使用该语法可在插入记录的时候先判断记录是否存在，如果不存在则插入，否则更新，很方便，无需执行两条SQLINSERT INTO osc_visit_stats(stat_date,type,id,view_count) VALUES (?,?,?,?) ON DUPLICATE KEY UPDATE view_count=view_count+? -- osc_visit_stats 表有复合主键 (stat_date,type,id)
INSERT INTO osc_space_visit_records(space,user,visit_count,ip,visit_time) VALUES(?,?,?,?,?) ON DUPLICATE KEY UPDATE visit_count=visit_count+1,ip=?,visit_time=NOW()
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