postgresql - 如何管理 sql 查询中的 NULL 字符串或日期 (PostgreSQL)

Question

PostgreSQL 11.1 对于下面的 sql 查询，其中 $1 和 $2 是字符串，$3 是时间戳，如何重写下面的查询，以便 $3 中的空值允许选择每个日期(不仅仅是空日期)。

   SELECT lastname, firstname, birthdate FROM patients 
           WHERE UPPER(lastname) LIKE UPPER($1)||'%' and UPPER(firstname) LIKE UPPER($2)||'%' AND birthdate::date = $3::date
        UNION
        SELECT lastname, firstname, birthdate FROM appointment_book 
           WHERE UPPER(lastname) LIKE UPPER($1)||'%' and UPPER(firstname) LIKE UPPER($2)||'$' and birthdate::date = $3::date

也就是说，如果 $3 为 null，那么这应该减少为:

SELECT lastname, firstname, birthdate FROM patients 
               WHERE UPPER(lastname) LIKE UPPER($1)||'%' and UPPER(firstname) LIKE UPPER($2)||'%' 
            UNION
            SELECT lastname, firstname, birthdate FROM appointment_book 
               WHERE UPPER(lastname) LIKE UPPER($1)||'%' and UPPER(firstname) LIKE UPPER($2)||'$' 

Answer 1

未经测试，但我认为您可以使用 CASE 表达式来处理它

SELECT lastname, firstname, birthdate FROM patients p
  WHERE UPPER(p.lastname) LIKE UPPER($1)||'%'
  AND   UPPER(p.firstname) LIKE UPPER($2)||'%'
  AND   (CASE WHEN $3 IS NULL THEN TRUE
         ELSE                      p.birthdate::date = $3::date
         END)
UNION
SELECT lastname, firstname, birthdate FROM appointment_book ab
  WHERE UPPER(ab.lastname) LIKE UPPER($1)||'%'
  AND   UPPER(ab.firstname) LIKE UPPER($2)||'%'
  AND   (CASE WHEN $3 IS NULL THEN TRUE
         ELSE                      ab.birthdate::date = $3::date
         END);