drop table computer_terms;
ERROR:  Relation 'computer_terms' does not exist
create table computer_terms(term text, category text, comments char(16));
create index computer_terms_index1 on computer_terms using btree(term);
create index computer_terms_index2 on computer_terms using btree(category);
insert into computer_terms values('computer display', 'X-A01-Y', 'a comment 1');
insert into computer_terms values('computer graphics', 'T-B01-Y', 'a comment 2');
insert into computer_terms values('computer programmer', 'S-Z01-Y', 'a comment 3');
vacuum computer_terms;
select * from computer_terms;
        term         | category |     comments     
---------------------+----------+------------------
 computer display    | X-A01-Y  | a comment 1     
 computer graphics   | T-B01-Y  | a comment 2     
 computer programmer | S-Z01-Y  | a comment 3     
(3 rows)

select * from computer_terms where category = 'X-A01-Y';
       term       | category |     comments     
------------------+----------+------------------
 computer display | X-A01-Y  | a comment 1     
(1 row)

select * from computer_terms where category ~* 'x-a01-y';
       term       | category |     comments     
------------------+----------+------------------
 computer display | X-A01-Y  | a comment 1     
(1 row)

select * from computer_terms where category like '_-A01-_';
       term       | category |     comments     
------------------+----------+------------------
 computer display | X-A01-Y  | a comment 1     
(1 row)

select * from computer_terms where category like '_-A%';
       term       | category |     comments     
------------------+----------+------------------
 computer display | X-A01-Y  | a comment 1     
(1 row)

select * from computer_terms where term ~ 'computer [dg]';
       term        | category |     comments     
-------------------+----------+------------------
 computer display  | X-A01-Y  | a comment 1     
 computer graphics | T-B01-Y  | a comment 2     
(2 rows)

select * from computer_terms where term ~* 'computer [DG]';
       term        | category |     comments     
-------------------+----------+------------------
 computer display  | X-A01-Y  | a comment 1     
 computer graphics | T-B01-Y  | a comment 2     
(2 rows)

select *,character_length(term) from computer_terms;
        term         | category |     comments     | char_length 
---------------------+----------+------------------+-------------
 computer display    | X-A01-Y  | a comment 1      |          16
 computer graphics   | T-B01-Y  | a comment 2      |          17
 computer programmer | S-Z01-Y  | a comment 3      |          19
(3 rows)

select *,octet_length(term) from computer_terms;
        term         | category |     comments     | octet_length 
---------------------+----------+------------------+--------------
 computer display    | X-A01-Y  | a comment 1      |           16
 computer graphics   | T-B01-Y  | a comment 2      |           17
 computer programmer | S-Z01-Y  | a comment 3      |           19
(3 rows)

select *,position('s' in term) from computer_terms;
        term         | category |     comments     | strpos 
---------------------+----------+------------------+--------
 computer display    | X-A01-Y  | a comment 1      |     12
 computer graphics   | T-B01-Y  | a comment 2      |     17
 computer programmer | S-Z01-Y  | a comment 3      |      0
(3 rows)

select *,substring(term from 10 for 4) from computer_terms;
        term         | category |     comments     | substr 
---------------------+----------+------------------+--------
 computer display    | X-A01-Y  | a comment 1      | disp
 computer graphics   | T-B01-Y  | a comment 2      | grap
 computer programmer | S-Z01-Y  | a comment 3      | prog
(3 rows)