为什么触发器在使用'inserted'表中的字段时尝试插入NULL值？

Question

我必须将MSSQL中完成的更改与远程MySQL数据库同步.要同步的更改是将发票和用户添加到系统.远程服务器不应该总是可以访问,所以我试图设置一种日志表来存储在MSSQL中完成的更改.

这是一个完全有效的触发器:

CREATE TRIGGER [dbo].[dokument_insert]
   ON [dbo].[dokument]
   AFTER INSERT
AS 
BEGIN
    SET NOCOUNT ON;
    INSERT INTO [bcg_ekodu].[dbo].[sync_stack] (event,sql, table_name, import_priority)
        SELECT 
            'INSERT',
            'INSERT INTO bills SET
                date = "'+CONVERT(VARCHAR(19),dok_kuup,120)+'", 
                total = "'+CAST(kokkusum AS nvarchar)+'",
                number = "'+RTRIM(dok_nr)+'", 
                created = "'+CONVERT(VARCHAR(19),savetime,120)+'", 
                rounded = "'+CAST(ymardus AS nvarchar)+'",
                currency = "'+CAST(valuuta AS nvarchar)+'", 
                due_date = "'+CONVERT(VARCHAR(19),tasupaev,120)+'", 
                pk_joosep = "'+CAST(dok_kood AS nvarchar)+'",
                joosep_hankija = "'+CAST(hankija AS nvarchar)+'";
             UPDATE
                bills, users, companies 
             SET 
                bills.user_id = users.id,
                bills.imported = NOW()
             WHERE
                bills.imported IS NULL
                AND companies.id = users.company_id
                AND companies.pk_joosep = 10
                AND bills.user_id = users.pk_joosep',
            'bills',
            '200'
        FROM inserted
END

每次将一行插入'dokument'表时,它会在'sync_stack'表中插入一行.'sql'列将包含一个SQL,用于在另一个(MySQL)数据库中创建相同类型的行.

但是这个触发器不起作用:

CREATE TRIGGER [dbo].[klient_insert]
   ON [dbo].[klient]
   AFTER INSERT
AS 
BEGIN
    SET NOCOUNT ON;
    INSERT INTO [bcg_ekodu].[dbo].[sync_stack] (event,sql, table_name, import_priority)
        SELECT 
            'INSERT',
            'INSERT INTO users SET
                username =10'+CAST(kl_kood as nvarchar)+',
                password = NULL,
                name ="'+LTRIM(RTRIM(kl_nimi))+'",  
                email ="'+CAST(LTRIM(RTRIM(kl_email)) as nvarchar)+'",  
                reference_no ="'+CAST(LTRIM(RTRIM(kl_viide)) as nvarchar)+'",   
                phone ="'+CAST(LTRIM(RTRIM(kl_tel1)) as nvarchar)+'",   
                logins ="'+CAST(0 as nvarchar)+'",  
                last_login = NULL,  
                created ="'+CONVERT(VARCHAR(19),savetime,120)+'",   
                updated = NULL, 
                deleted ="0",   
                address ="'+CAST(LTRIM(RTRIM(kl_aadr1)) as nvarchar)+'",    
                pk_joosep ="'+CAST(kl_kood as nvarchar)+'"',
            'users',
            '210'
        FROM inserted
END

虽然上面的SQL创建触发器执行完成就好了,当我尝试了一些行插入到"触发"表中,我得到以下错误:

No row was updated.

The data in row 175 was not committed.
Error Source: .Net SqlClient Data Provider.
Error Message: Cannot insert the value NULL into column 'sql', table 'mydb.dbo.sync_stack'; column does not allow nulls. INSERT fails.

The statement has been terminated.

Correct the errors and retry or press ESC to cancel the change(s).

• 如果我删除此触发器,则不会发生此错误.
• 如果我只插入'sql'列的纯文本,它按预期工作.
• 如果我使用插入行中的任何字段,即使只是一个文本字段,它也会再次失败.
• 如果我在'sql'列中允许NULL值,插入行成功但我在'sql'列中得到NULL值.

如何让第二个触发器按预期工作？

Answer 1

我怀疑你插入的至少一个插入到SQL语句中的值是NULL.你可以通过使用COALESCE,例如,

username =10'+COALESCE(CAST(kl_kood as nvarchar), '')+',

当然,如果不nvarchar指定长度,你不应该声明,对吗？

• 糟糕的习惯:没有(长度)声明VARCHAR