Want to create a database column with following checks on oracle database sql

See if this helps.

SQL> create table test
  2    (col  varchar2(20),
  3     --
  4     constraint ch1_upper check (col = upper(col)),
  5     --
  6     constraint ch2_letraspc check (col = trim(col)),
  7     --
  8     constraint ch3_wrdspc check (regexp_like(col, '^ *(\w+ ?)+ *$')),
  9     --
 10     constraint ch4_spec check (regexp_like(col, '^[[:alpha:] ]+$'))
 11    );

Table created.

Testing:

SQL> insert into test values ('abc');
insert into test values ('abc')
*
ERROR at line 1:
ORA-02290: check constraint (SCOTT.CH1_UPPER) violated


SQL> insert into test values (' DEF');
insert into test values (' DEF')
*
ERROR at line 1:
ORA-02290: check constraint (SCOTT.CH2_LETRASPC) violated


SQL> insert into test values ('DEF ');
insert into test values ('DEF ')
*
ERROR at line 1:
ORA-02290: check constraint (SCOTT.CH2_LETRASPC) violated


SQL> insert into test values (' DEF ');
insert into test values (' DEF ')
*
ERROR at line 1:
ORA-02290: check constraint (SCOTT.CH2_LETRASPC) violated


SQL> insert into test values ('GHI23');
insert into test values ('GHI23')
*
ERROR at line 1:
ORA-02290: check constraint (SCOTT.CH4_SPEC) violated


SQL> insert into test values ('GHI#');
insert into test values ('GHI#')
*
ERROR at line 1:
ORA-02290: check constraint (SCOTT.CH4_SPEC) violated


SQL> insert into test values ('GHI   JKL');
insert into test values ('GHI   JKL')
*
ERROR at line 1:
ORA-02290: check constraint (SCOTT.CH3_WRDSPC) violated


SQL> insert into test values ('GHI JKL    MNO');
insert into test values ('GHI JKL    MNO')
*
ERROR at line 1:
ORA-02290: check constraint (SCOTT.CH3_WRDSPC) violated


SQL> insert into test values ('GHI JKL MNO');

1 row created.

SQL>