Question

我们在decimal（20,5）类型的数据库中有一个货币字段。如何将CAST或COnvert添加到传出的Nhibernate标准？

   SELECT
        TOP (1000)  this_.DepositAccountId as DepositA1_71_0_,
        this_.BranchId as BranchId71_0_,
        this_.ConfigurationStatusId as Configu14_71_0_,
        this_.ConfiguredBy as Configu41_71_0_,
        this_.ConfiguredDate as Configu15_71_0_,
        this_.DepositAccountBalance as DepositA9_71_0_
    FROM
        dbo.DepositAccount this_ 
    WHERE
        Convert(Decimal(20,2), this_.DepositAccountBalance) = 1.01

目前它像这样发送WHERE子句

WHERE
           this_.DepositAccountBalance = 1.01

我需要添加转换或转换或舍入。

数据库中有一条记录，其中DepositAccountBalance = 1.0107。因此，如果没有Cast或Convert，则没有匹配项。

网站上有一些资源可供人们添加精度，缩放到生成的.hbm.xml。其中一些人建议使用Nhibernate Dialect和自定义SQL函数

有谁可以解释我需要哪一个？我什么时候使用Nhibernate Dialect。我何时将精度添加到.hbm.xml。我需要做的就是在where子句

中添加Convert或round

Answer 1

所以应该工作（我已经大大简化了查询，但问题都是一样的）：

IType decimalType = TypeFactory.Basic("decimal(20,2)");

IProjection castProjection = Projections.Cast(
    decimalType,
    Projections.Property<DepositAccount>(acct => acct.DepositAccountBalance));

var accounts = session.QueryOver<DepositAccount>()
    .Where(Restrictions.Eq(castProjection, 1.01))
    .List<DepositAccount>();

不幸的是，这会生成以下SQL：

SELECT         
    this_.*
FROM         
    DepositAccount this_     
WHERE         
    cast( this_.DepositAccountBalance as DECIMAL(19,5)) = 1.01

咦？我们刚刚指定我们想要一个类型decimal(20,2)！发生了什么事？

看起来CastProjection完全忽略了传递它的类型的精度和比例。这是CastProjection类的相关代码：

public override SqlString ToSqlString(ICriteria criteria, int position, ICriteriaQuery criteriaQuery, IDictionary<string, IFilter> enabledFilters)
{
    ISessionFactoryImplementor factory = criteriaQuery.Factory;
    SqlType[] sqlTypeCodes = type.SqlTypes(factory);
    if (sqlTypeCodes.Length != 1)
    {
        throw new QueryException("invalid Hibernate type for CastProjection");
    }

    // HERE: precision and scale are being ignored.
    string sqlType = factory.Dialect.GetCastTypeName(sqlTypeCodes[0]);
    int loc = position*GetHashCode();
    SqlString val = projection.ToSqlString(criteria, loc, criteriaQuery,enabledFilters);
    val = SqlStringHelper.RemoveAsAliasesFromSql(val);

    return new SqlString("cast( ", val, " as ", sqlType, ") as ", GetColumnAliases(position, criteria, criteriaQuery)[0]);
}

对于所有GetCastTypeName类型，decimal(19,5)只返回decimal，这似乎是一个错误。

有两种方法可以解决这个问题：

使用Projections.SqlFunction（推荐 - 不知道＃2的后果是什么）

要做到这一点，我们只需要使用Projections.SqlFunction明确为我们执行cast：

var decimalType = TypeFactory.Basic("decimal(20,2)");

var castProjection = Projections.SqlFunction(
    new SQLFunctionTemplate(decimalType, "cast(?1 as decimal(20,2))"),
        decimalType,
        Projections.Property<DepositAccount>(acct=> acct.DepositAccountBalance));

var q = session.QueryOver<DepositAccount>()
    .Where(Restrictions.Eq(castProjection, 1.01))
    .List<DepositAccount>();

这会生成预期的SQL：

SELECT        
    this_.* 
FROM         
    DepositAccount this_     
WHERE         
    cast(this_.DepositAccountBalance as decimal(20,2)) = 1.01

编写我们自己的类来正确进行强制转换。我们实际上只需要更改一行代码就可以使其工作。否则它与CastProjection类完全相同：

public class PrecisionCast : SimpleProjection 
{
    private readonly IType type;
    private readonly IProjection projection;

    public PrecisionCast(IType type, IProjection projection)
    {
        this.type = type;
        this.projection = projection;
    }

    public override bool IsAggregate
    {
        get { return false; }
    }

    public override SqlString ToSqlString(ICriteria criteria, int position, ICriteriaQuery criteriaQuery, IDictionary<string, IFilter> enabledFilters)
    {
        ISessionFactoryImplementor factory = criteriaQuery.Factory;
        SqlType[] sqlTypeCodes = type.SqlTypes(factory);


        if (sqlTypeCodes.Length != 1)
        {
            throw new QueryException("invalid Hibernate type for CastProjection");
        }       

        // Get the type name, preserving scale and precision
        string sqlType = factory.Dialect.GetTypeName(sqlTypeCodes[0]);

        int loc = position*GetHashCode();
        SqlString val = projection.ToSqlString(criteria, loc, criteriaQuery,enabledFilters);
        val = SqlStringHelper.RemoveAsAliasesFromSql(val);

        return new SqlString("cast( ", val, " as ", sqlType, ") as ", GetColumnAliases(position, criteria, criteriaQuery)[0]);
    }

    public override IType[] GetTypes(ICriteria criteria, ICriteriaQuery criteriaQuery)
    {
        return new IType[]{ type };
    }

    public override NHibernate.Engine.TypedValue[] GetTypedValues(ICriteria criteria, ICriteriaQuery criteriaQuery)
    {
        return projection.GetTypedValues(criteria, criteriaQuery);
    }

    public override bool IsGrouped
    {
        get
        {
            return projection.IsGrouped;
        }
    }

    public override SqlString ToGroupSqlString(ICriteria criteria, ICriteriaQuery criteriaQuery, IDictionary<string, IFilter> enabledFilters)
    {
        return projection.ToGroupSqlString(criteria, criteriaQuery, enabledFilters);
    }
}

然后像这样使用它：

var decimalType = TypeFactory.Basic("decimal(20,2)");

var castProjection = new PrecisionCast(
    decimalType, Projections.Property<DepositAccount>(acct => acct.DepositAccountBalance));

var accounts = session.QueryOver<DepositAccount>()
    .Where(Restrictions.Eq(castProjection, 1.01))
    .List<DepositAccount>();

这似乎解决了decimal类型的问题，但我不知道其他类型的后果是什么，因此不保证此代码。

希望这会有所帮助。我和＃1一起去。

Nhibernate方言，精确铸造小数从5位到2位

1 个答案: