security-admin/db/oracle/patches/023-add-unique-constraint-on-table-x_user.sql

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--     http://www.apache.org/licenses/LICENSE-2.0
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DECLARE
	v_count number:=0;
BEGIN
  	select count(*) into v_count from user_tab_cols where table_name='X_USER' and column_name='USER_NAME';
  	if (v_count = 1) then
  		v_count:=0;
  		select count(*) into v_count from user_constraints where table_name='X_USER' and constraint_name='X_USER_UK_USER_NAME' and constraint_type='U';
		if (v_count = 0) then
			v_count:=0;
			select count(*) into v_count from user_ind_columns WHERE table_name='X_USER' and column_name='USER_NAME' and index_name='X_USER_UK_USER_NAME';
			if (v_count = 0) then
				execute immediate 'ALTER TABLE x_user MODIFY(user_name VARCHAR(767)) ADD CONSTRAINT x_user_UK_user_name UNIQUE (user_name)';
			end if;
			commit;
		end if;
	end if;
end;/