主键、唯一键约束、唯一索引区别之创建
主键、唯一键约束、唯一索引区别之删除
一：查看唯一键、主键及索引的情况
SCOTT@ORA11GR2>select table_name,column_name,constraint_name from user_cons_columns where table_name=upper('student');
TABLE_NAME COLUMN_NAME CONSTRAINT_NAME
--------------- --------------- --------------------
STUDENT SNAME UK_STUDENT_SNAME
STUDENT SNO PK_STUDENT_SNO
SCOTT@ORA11GR2>
SCOTT@ORA11GR2>select table_name,column_name,index_name from user_ind_columns where table_name=upper('student');
TABLE_NAME COLUMN_NAME INDEX_NAME
--------------- --------------- ------------------------------
STUDENT SNAME UK_STUDENT_SNAME
STUDENT SNO PK_STUDENT_SNO
STUDENT IDCARD UIDX_STUDENT_IDCARD
SCOTT@ORA11GR2>
二：删除唯一键、主键及索引
SCOTT@ORA11GR2>alter table student drop constraint uk_student_sname;
Table altered.
SCOTT@ORA11GR2>alter table student drop primary key;
Table altered.
SCOTT@ORA11GR2>
SCOTT@ORA11GR2>drop index uidx_student_idcard;
Index dropped.
SCOTT@ORA11GR2>
三：再次查看唯一键、主键及索引
SCOTT@ORA11GR2>select table_name,column_name,constraint_name from user_cons_columns where table_name=upper('student');
no rows selected
SCOTT@ORA11GR2>select table_name,column_name,index_name from user_ind_columns where table_name=upper('student');
no rows selected
SCOTT@ORA11GR2>
小结：
当主键、唯一键删除的时候，一并把它们自动创建的索引也一并删除
唯一索引，则直接将索引删除，没什么异议
来自 “ ITPUB博客 ” ，链接：https://blog.itpub.net/685769/viewspace-743403/ ，如需转载，请注明出处，否则将追究法律责任。
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