来自文档（我的）：

IF search_condition THEN statement_list
    [ELSEIF search_condition THEN statement_list] ...
    [ELSE statement_list]
END IF

每个 statement_list 由一个或多个sql语句组成；空的 statement_list 不允许。

else块为空，这在mysql中是不允许的。您应该从代码中删除关键字else，如下所示：

DELIMITER $$

CREATE TRIGGER bm_keuangan 
AFTER UPDATE ON pembayaran_project FOR EACH ROW
BEGIN
DECLARE nama_project varchar(100);
DECLARE cek_di_keuangan varchar(100);
IF (!(isnull(NEW.deleted_at))) THEN
    UPDATE keuangan SET keuangan.deleted_at = now() WHERE keuangan.ref = NEW.id AND keuangan.jk_id = 5;

END IF;

END $$
DELIMITER ;