oracle外键约束，无法truncate table的时候

不少人在遇到这个情况下会找到这么样的一个sql脚本：查询外键

查找表的外键（包括名称，引用表的表名和对应的键名，下面是分成多步查询）：

select * from user_constraints c where c.constraint_type = 'R' and c.table_name = 要查询的表

查询外键约束的列名：

select * from user_cons_columns cl where cl.constraint_name = 外键名称

查询引用表的键的列名：

select * from user_cons_columns cl where cl.constraint_name = 外键引用表的键名

然后可能是0行受影响！！！！

那么这时候解决的办法：

1，不要用truncate table 改用delete

2，试试这个：禁用外键关系

①执行脚本，禁用外键

BEGIN
for c in (select 'ALTER TABLE '||TABLE_NAME||' DISABLE CONSTRAINT '||constraint_name||' ' as v_sql from user_constraints where CONSTRAINT_TYPE='R') loop
 
 EXECUTE IMMEDIATE c.v_sql;
  
 
end loop;
end;

②一次性删除

begin
   for ec in
     (select table_name from user_tables)
     loop
       execute immediate 'delete '|| ec.table_name;
     end loop;
 end;

③再次启用外键

BEGIN
for c in (select 'ALTER TABLE '||TABLE_NAME||' ENABLE CONSTRAINT '||constraint_name||' ' as v_sql from user_constraints where CONSTRAINT_TYPE='R') loop
 
 EXECUTE IMMEDIATE c.v_sql;
  
 
end loop;
end;

------------------------------------------------------------------------------------------------------------------------------------------------------------

补充：启用外键的时候，如果用步骤③无效的话，那么我们需要手动启用外键！

select 'alter table '||table_name||' enable constraint '||constraint_name||';' from user_constraints where constraint_type='R'  

调用这个时候会得到：

alter table T_DATAMODELEXTENDFIELD enable constraint FK_DATAMODELEXTENDWIDGETID;
alter table T_POWER_MAPPER enable constraint FK7865B8A6C505DDD;
alter table T_ADMINUSER_MAPPER enable constraint FKCC6502F11FB6F528;
alter table T_SYSTEM_TREENODE enable constraint TREENODE_PID;
alter table T_DATA_TREE_MAPPER enable constraint T_DATA_T_REFERENCE_T_SYSTEM;
alter table T_SYSTEM_TREENODE enable constraint T_SYSTEM_REFERENCE_T_SYSTEM;
alter table T_ANSWER enable constraint FK5F4291E99020211D;
alter table T_POWER_POINT enable constraint FK1CD8FA8B2EB2BE67;
alter table T_OPERATE_LOG enable constraint FKF5C6CABE16D04B87;
alter table T_POWER_MAPPER enable constraint FK7865B8A6531B82E2;
alter table T_FEEDMODULE_TYPE_MAPPER enable constraint FK4575CFDC303E350E;
alter table T_FEEDBACK_ANSWER enable constraint FKE54C2FED7FFDB5CE;
alter table T_FAVORITE enable constraint FKF54E3D078EBBFDB5;
alter table T_FAVORITE_TYPE enable constraint FK54731772C1EDF96B;
alter table T_EMAIL_USER_MAPPER enable constraint FK178A5A079AA6A005;
alter table T_D_MANUALS enable constraint FK_TD_MANUALS_ZHONGD;
alter table T_D_STRATEGY enable constraint FK_STRATEGY_RAIDERTYPE;
alter table T_D_CZSTEP enable constraint FK_TD_CZSTEP_T_PROCESS;
alter table T_DOC_POWER_MAPPER enable constraint FK8CECEACD8D4BBF79;
alter table T_CMS_CLASS enable constraint FK1B67ACF760A36168;
alter table T_DATAMODELEXTENDFIELD enable constraint FK_EXTENDWIDGETDATAMODELID;
alter table T_COORDINATE enable constraint T_COORDI_REFERENCE_T_COORDI;
alter table T_CMS_USER enable constraint FK_CMS_USER_LEVEL;
alter table T_CMS_USER enable constraint FK_CMS_USER_USERGROUPID;
alter table T_CMS_USER_GROUP enable constraint FK_USERGROUP_PID;
alter table T_DOC_POWER_MAPPER enable constraint FK8CECEACD76E86716;
alter table T_COORDINATE_MAPPER enable constraint FK_T_COORDI_REFERENCE_T_CMS_US;
alter table T_FAVORITE enable constraint FK_FAVORITE_USERID;
alter table T_CMS_USER_JIFEN_LOG enable constraint FK74A9BC62835201B2;
alter table T_ANSWER enable constraint FK5F4291E92E8E5B29;
alter table T_QUESTION enable constraint FK712EAF512E8E5B29;
alter table T_DYNAMICS enable constraint FKCB31B7F2E8E5B29;
alter table T_BLOG enable constraint FKCB5B108D2E8E5B29;
alter table T_DISCUSS_CONTENT enable constraint FK47DE3D4F2E8E5B29;
alter table T_DOCS enable constraint FK_TDOCS_USERID;
alter table T_LETTER enable constraint FK718976511AF48B53;
alter table T_USER_FRIEND enable constraint FKCF0AA247B91113C;
alter table KM_DOCS enable constraint FKDBA4DAF82E8E5B29;
alter table T_EMAIL_USER_MAPPER enable constraint FK178A5A072E8E5B29;
alter table T_DOC_POWER_MAPPER enable constraint FK8CECEACD14EC0B48;
alter table T_CMS_CLASS enable constraint FK_CMSCLASSSITEID;
alter table T_DATAMODEL enable constraint FK9FC3FB42A9D5321;
alter table T_CMS_CLASS enable constraint FK_CMSCLASSPID;
alter table T_COORDINATE enable constraint FKC938BA234F395E2E;
alter table T_ZHUI_WEN enable constraint FK831F874E1944206;
alter table T_QUESTION enable constraint FK712EAF519BEA7A31;
alter table T_D_STRATEGY enable constraint FK_STRATEGY_ADMINUSER;
alter table KM_CONTENT_VERSIONS enable constraint FK2D4AF8DE318963AE;
alter table KM_CONTENT_VERSIONS enable constraint FK2D4AF8DEA4DF1815;
alter table KM_CONTENT_VERSIONS enable constraint FK2D4AF8DEA72909F0;
alter table KM_CONTENT enable constraint FK11C669C318963AE;
alter table KM_CONTENT enable constraint FK11C669CA4DF1815;
alter table KM_TREE enable constraint FKDBAC2C5B394AD71B;
alter table KM_TREE_COORDINATE enable constraint FK_KM_TREE__REFERENCE_KM_TREE;
alter table KM_TOOLBAR enable constraint FK8470BD9EEA9BA8F8;
alter table KM_NOTICE enable constraint FK96F2145555561879;
alter table KM_GUZHANG enable constraint FKDF95FDE155561879;
alter table KM_NOTICE enable constraint FK96F2145560DD35CD;
alter table KM_GUZHANG enable constraint FKDF95FDE160DD35CD;
alter table KM_DOC_MAPPER enable constraint FK7BB1DE253EF6F880;
alter table KM_CONTENT enable constraint FK11C669C664239CA;

然后执行上面的脚本就可以启用外键约束了！！！！！

Tips：删除外键或者禁用外键的sql脚本

删除外键： 关键字 drop constraiint

select 'alter table '||table_name||' drop constraint '||constraint_name||';' from user_constraints where constraint_type='R' 

禁用外键：关键字disable constraint

select 'alter table '||table_name||' disable constraint '||constraint_name||';' from user_constraints where constraint_type='R'

@date：2014年1月15日