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摘要： join的类型1．内联结：将两个表中存在联结关系的字段符合联结关系的那些记录形成记录集的联结。2．外联结：分为外左联结和外右联结。案例背景create table java (name varchar(255));insert into java values ('java1'),('java2'),('blue'); create table mysql (name varchar(255));insert into mysql values ('mysql1'),('mysql2'),('blue 阅读全文

摘要： delete语法单表语法：DELETE [LOW_PRIORITY] [QUICK] [IGNORE] FROM tbl_name [WHERE where_definition] [ORDER BY ...] [LIMIT row_count]多表语法：DELETE [LOW_PRIORITY] [QUICK] [IGNORE] tbl_name[.*] [, tbl_name[.*] ...] FROM table_references [WHERE where_definition]或DELETE [LOW_PRIORITY] [QUICK] [IGN... 阅读全文

摘要： update语法Single-table语法：UPDATE [LOW_PRIORITY] [IGNORE] tbl_name SET col_name1=expr1 [, col_name2=expr2 ...] [WHERE where_definition] [ORDER BY ...] [LIMIT row_count]Multiple-table语法：UPDATE [LOW_PRIORITY] [IGNORE] table_references SET col_name1=expr1 [, col_name2=expr2 ...] [WHERE wh... 阅读全文