相关疑难解决方法(0)

在MySQL中JOIN,ON和之间有什么区别USING()？据我所知,USING()只是更方便的语法,而ON当列名不相同时允许更多的灵活性.然而,这种差异是如此微小,你会认为他们只是消失了USING().

除此之外还有更多的东西吗？如果是,我应该在特定情况下使用哪个？

我正在尝试这样的查询:

DELETE FROM term_hierarchy AS th
WHERE th.parent = 1015 AND th.tid IN (
    SELECT DISTINCT(th1.tid)
    FROM term_hierarchy AS th1
    INNER JOIN term_hierarchy AS th2 ON (th1.tid = th2.tid AND th2.parent != 1015)
    WHERE th1.parent = 1015
);

你可以告诉我,如果同一个tid有其他父母,我想删除1015的父关系.但是,这会产生语法错误:

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'AS th
WHERE th.parent = 1015 AND th.tid IN (
  SELECT DISTINCT(th1.tid)
  FROM ter' at line …

我想从表中删除取决于另一个引用第一个表的表上存在的数据,但是,我有代码可以工作并显示当我将其作为SELECT stetement运行时要删除的值,但是当我将其更改为删除它给了我错误,我不明白为什么他们在那里.

DELETE leadCustomer.* FROM coursework.leadCustomer LEFT JOIN coursework.flightBooking
ON leadCustomer.customerID = flightBooking.customerID
WHERE leadCustomer.customerID NOT IN (
SELECT customerID FROM (SELECT customerID, status FROM coursework.flightBooking) AS
StatusCount where status IN  ('R','H') GROUP BY customerID
)
AND leadCustomer.customerID = 8;

错误:

ERROR:  syntax error at or near "leadCustomer"
LINE 1: DELETE leadCustomer.* FROM coursework.leadCustomer LEFT JOIN...
               ^

********** Error **********

ERROR: syntax error at or near "leadCustomer"
SQL state: 42601
Character: 8

我正在使用postgres

我有以下实体:

我想使用JPA删除用户的id和用户名的WordSet.

这是实体声明:

用户

@Entity
@Data
@ToString(callSuper = true)
@EqualsAndHashCode(callSuper = true)
@AllArgsConstructor
@NoArgsConstructor
public class User extends AbstractModelClass {

    private String name;
    private String username;
    private String password;
    private String email;

    @ManyToMany(fetch = FetchType.EAGER)
    private Set<Role> roles;
}

UserDictionary

@Entity
@Data
@ToString(callSuper = true)
@EqualsAndHashCode(callSuper = true)
@AllArgsConstructor
@NoArgsConstructor
public class UserDictionary extends AbstractModelClass {

    @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL, mappedBy = "userDictionary")
    private Set<WordSet> wordSets;

    @OneToOne(cascade = CascadeType.ALL)
    private User user;

    @PrePersist
    private void addDictionaryToWordSets() {
        wordSets.forEach(wordSet …

为什么会出现语法错误

DELETE FROM `print_mailing_request` pmr
INNER JOIN `person` p
  ON p.id = pmr.person AND p.email LIKE '%@TEST.COM'
WHERE 
pmr.sent_to_fulfiller != 'y'

什么时候正常工作没有错误？

SELECT * FROM `print_mailing_request` pmr
INNER JOIN `person` p
  ON p.id = pmr.person AND p.email LIKE '%@TEST.COM'
WHERE 
pmr.sent_to_fulfiller != 'y'