postgresql类型转换

作者: 爱吃h泡菜o221呃呃答天我
来源: 51数据库
2020-09-29

postgres=# create table t (id varchar);CREATE TABLEpostgres=# insert into t values ('1');INSERT 0 1postgres=# CREATE FUNCTION varcharinteq(varchar,int) RETURNS booleanpostgres-# AS $$ SELECT $1=$2::varchar $$postgres-# LANGUAGE SQL;CREATE FUNCTIONpostgres=# create operator = (procedure=varcharinteq,LEFTARG='varchar',RIGHTARG='int4');CREATE OPERATORpostgres=# select * from t where id=1; id ---- 1(1 row)postgres=# CREATE FUNCTION intvarchareq(int,varchar) RETURNS boolean AS $$ SELECT $1::varchar=$2 $$ LANGUAGE SQL;CREATE FUNCTIONpostgres=# create operator = (procedure=intvarchareq,LEFTARG='int4',RIGHTARG='varchar');CREATE OPERATORpostgres=# select * from t where 1=id; id ---- 1(1 row)

　　回复 digoal 多谢，看来相当复杂

　　看来9还反而严格了..

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