Question

我有以下SQL语句。我想要做的是包括一个IF语句，以涵盖其中一列返回0或空白结果的可能性，没有0 ID。在这种情况下，我试图涵盖magez_cfv_nations结果可能返回零或空白结果的可能性。

SELECT c.clan_name, n.nation_name, 
    CONCAT(r.rarity_shorthand, " - ", r.rarity_name) AS rarity_text, 
    t.trigger_name, s.skill_name
 FROM `magez_cfv_cards` AS cards
 JOIN `magez_cfv_clans` c ON cards.clan_id = c.clan_id
 JOIN `magez_cfv_nations` n ON cards.nation_id = n.nation_id
 JOIN `magez_cfv_rarity` r ON cards.rarity_id = r.rarity_id
 JOIN `magez_cfv_trigger` t ON cards.trigger_id = t.trigger_id
 JOIN `magez_cfv_skills` s ON cards.skill_id = s.skill_id

Answer 1

您需要LEFT JOIN

LEFT JOIN关键字返回左表中的所有行（table_name1），即使右表中没有匹配项

试试这个

SELECT c.clan_name, n.nation_name, 
    CONCAT(r.rarity_shorthand, " - ", r.rarity_name) AS rarity_text, 
    t.trigger_name, s.skill_name
 FROM `magez_cfv_cards` AS cards
 JOIN `magez_cfv_clans` c ON cards.clan_id = c.clan_id
 LEFT JOIN `magez_cfv_nations` n ON cards.nation_id = n.nation_id
 JOIN `magez_cfv_rarity` r ON cards.rarity_id = r.rarity_id
 JOIN `magez_cfv_trigger` t ON cards.trigger_id = t.trigger_id
 JOIN `magez_cfv_skills` s ON cards.skill_id = s.skill_id

Answer 2

您应该使用的函数是IIF()，其语法是

IIF([condition],[if true],[if false])

在MySQL中使用IF语句

2 个答案: