可以使用SQL约束来防止条件成立时更改特定值吗？

CREATE TABLE example_table (
    id INT PRIMARY KEY,
    column_name VARCHAR(255),
    value_to_check INT,
    CONSTRAINT check_value CHECK (
        (column_name = 'condition_met' AND value_to_check = 1) OR
        (column_name != 'condition_met')
    )
);

CREATE TABLE example_table (
    id INT PRIMARY KEY,
    column_name VARCHAR(255),
    value_to_check INT
);

CREATE OR REPLACE FUNCTION check_value_function()
RETURNS TRIGGER AS $$
BEGIN
    IF NEW.column_name = 'condition_met' AND NEW.value_to_check != 1 THEN
        RAISE EXCEPTION '当column_name为"condition_met"时，value_to_check的值必须为1';
    END IF;
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER check_value_trigger
BEFORE INSERT OR UPDATE ON example_table
FOR EACH ROW
EXECUTE FUNCTION check_value_function();