oracle中的KEY关键字有什么用？ postgresql 中的 KEY 是否有任何替代方案

Question

What is the use of KEY keyword in oracle.what is the equivalent for this keyword in postgresql?this is a sample code from a function mentioned in package.here.KEY is not known one because this is writter years ago, cursor variable is not supported in postgres,what are the equivalent for migrating this code to postgresql

Code:

create or replace

function Rate ( p_base_curr CHAR ,

p_orig_curr CHAR ,

p_time_string CHAR ,

p_rate_type CHAR ) returns INT as $$ declare rate INT;

 

LoI INTEGER;

 

HiI INTEGER;

 

mI INTEGER;

 

mKey VARCHAR (30);

 

mLKey VARCHAR (30);

 

i INTEGER;

 

cursor get_rates_c is

select

       ( TRIM (e.frk_category) || TRIM (e.fk_prim_currency) || TRIM (e.fk_scndry_currency) || TRIM (e.time_string) ) key ,

       ( e.primary_units / e.secondary_units ) Rate ,

       e.to_time_string ToTS

from

       xxx e

where

       e.to_time_string >= TRIM ( TO_CHAR ( TO_NUMBER ( TO_CHAR ( SYSDATE,

       'YYYY' ) ) - Years_To_Cache ,

       '9999' ) )

order by

       ( TRIM (e.frk_category) || TRIM (e.fk_prim_currency) || TRIM (e.fk_scndry_currency) || TRIM (e.time_string) ) desc;

 

type rates_t is VARRAY (120000) of get_rates_c%ROWTYPE;

 

rates rates_t;

 

begin if p_base_curr = p_orig_curr then rate := 1;

else mLKey := TRIM (p_base_curr) || TRIM (p_orig_curr) || TRIM (p_rate_type);

 

mKey := mLKey || TRIM (p_time_string);

 

LoI := 1;

 

HiI := rates.COUNT;

 

while LoI <= HiI loop mI := ( LoI + HiI ) / 2;

--    EXIT WHEN rates ( mI ).KEY = mKey;

case

       when rates (mI).key < mKey then LoI := mI + 1;

else HiI := mi - 1;

end if;

end loop;

 

if ( rates (mi).key <= mKey )

and ( SUBSTR ( rates (mi).key ,

1 ,

LENGTH (mLKey) ) = mLKey )

and ( p_time_string <= rates (mi).ToTS ) then rate := rates (mi).rate;

else begin

-- SQLINES LICENSE FOR EVALUATION USE ONLY

select

       coalesce ( ( e.primary_units / e.secondary_units ),

       -1 )

into

       RATE

from

       xxx e

where

       e.fk_prim_currency = p_base_curr

       and e.fk_scndry_currency = p_orig_curr

       and p_time_string between e.time_string and e.to_time_string

       and e.frk_category = p_rate_type;

 

exception

when others then rate := -1;

end;

end if;

end if;

 

case

       when rate = -1 then

       case

              when Return_Zero_On_Missing = 1 then rate := 0;

else

end;

 

$$ language plpgsql;

 

if;

end if;

 

return rate;

end Rate;

Answer 1

It isn't a keyword in this context. You were referring to the use at:

exit when rates(mi).KEY = mKey;

Where rates is defined with:

type rates_t is VARRAY (120000) of get_rates_c%ROWTYPE;
rates rates_t;

The use of ROWTYPE means that each element of the array is a record with the same structure as a row returned by the get_rates_c cursor, which is:

cursor get_rates_c is
select
       ( TRIM (e.frk_category) || TRIM (e.fk_prim_currency) || TRIM (e.fk_scndry_currency) || TRIM (e.time_string) ) key ,
       ( e.primary_units / e.secondary_units ) Rate ,
       e.to_time_string ToTS
from
       xxx e
...

So rates(mi).key is the value constructed from ( TRIM (e.frk_category) || TRIM (e.fk_prim_currency) || TRIM (e.fk_scndry_currency) || TRIM (e.time_string) ) for the corresponding row from that cursor query.

So, it isn't a keyword, it's the column alias from your cursor query.