我想做一个需要两个表的查询。查询的目的是返回treduit或tplein列（在表tarif中）的值，具体取决于grilletarif和iduser列（表client）中写入的内容。
第一个表：客户端

nom   prenom     mail          adresse              idUser                            grilleTarif
 admin admin admin@admin.com 10 rue de l'admin m(à"éàé"àé'à_ç-&'à&&=&-&é&à&&&é(è&é_è(§ tPlein

第二张table：tarif

tReduit tPlein nomActivity nPlace 
2        3      NULL       NULL 
7        8      aquaPoney  10

我的问题：

SELECT
    tarif.tReduit, 
    tarif.tPlein, 
    client.grilleTarif, 
    CASE grilleTarif 
        WHEN 'tReduit' 
            THEN tarif.tReduit 
        WHEN 'tPlein' 
            THEN tarif.tPlein
        ELSE tarif.tPlein
        END AS X
FROM tarif, client 
WHERE client.idUser = m(à"éàé"àé'à_ç-&'à&&=&-&é&à&&&é(è&é_èpp§, tarif.nomActivity IS NULL;

我执行它时出现语法错误。

# 1064 - You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'CASE grilleTarif WHEN 'tReduit' then tarif.tReduit when 'tPlein' then tarif.tPle' at line 1.

Unrecognized keyword. (near "AS" at position 153)
Unexpected token.(near "tarif" at position 156)
Unexpected token. (near "." at position161) 
Unexpected token. (near "tPlein" at position 162)

我尝试执行的另一个查询是如何在动态查询中将行值连接到列名

SELECT grilleTarif FROM client c
    INNER JOIN 
    ( SELECT tarifCol, tarif from tarif t
        unpivot 
        (
              tarif
              for tarifCol in ([tPlein], [tReduit]) 

        ) unpiv
    ) d
         on c.grilleTarif=t.tarifCol 
where c.idUser = m(à"éàé"àé'à_ç-&'à&&=&-&é&à&&&é(è&é_è(§
and t.nomActivity is NULL;

我还有语法错误#1064

[...]near 'unpivot (tarif for tarifCol in ([tPlein], [tReduit])) unpiv )
Unexpected character. (near "[" at position 114)
Unexpected character. (near "]" at position 121)
Unexpected character. (near "[" at position 124)
Unexpected character. (near "]" at position 132)