在Postgres我试图返回值，但它显示错误

Question

在postgres中我试图返回此但它显示错误

select substr('10111',3,1) as aa_code
return aa_code;


ERROR:  syntax error at or near "return"
LINE 2:  return aa_code;
         ^
********** Error **********

Answer 1

为什么要使用退货？

=# select substr('10111',3,1) as aa_code;
 aa_code
---------
 1
(1 row)