2024年4月15日发(作者：)

--------+----------------+-----------

item | inventory_item |

count | integer |

postgres=# select item from on_hand ;

item

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

("fuzzy dice",42,1.99)

(Apple,22,4.4)

(Apple,22,4.4)

(Apple,22,4.4)

(Orange,22,55)

(Orange1,22,66)

(6 rows)

postgres=# select (item).name from on_hand where (item).price >10;

name

---------

Orange

Orange1

(2 rows)

postgres=# select (item).name from on_hand ;

name

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

fuzzy dice

Apple

Apple

Apple

Orange

Orange1

(6 rows)

postgres=# select (on_).name from on_hand where (on_).price > 10;

name

---------

Orange

Orange1

(2 rows)

select just one field from the result of a function that returns a composite value,you'd need to

write something like:

select (my_func(...)).field from table_name;

postgres=# create table complex_col (col complex);

CREATE TABLE

postgres=# insert into complex_col values ((1.1,2.2));

INSERT 0 1

postgres=# insert into complex_col (col.r,col.i) values (8.8,9.9);

INSERT 0 1

postgres=# select * from complex_col ;

col

-----------

(1.1,2.2)

(8.8,9.9)

(2 rows)