Skip to content

表达式函数

28810 edited this page Dec 8, 2019 · 36 revisions

这是 FreeSql 非常特色的功能之一,深入细化函数解析,所支持的类型基本都可以使用对应的表达式函数,例如 日期、字符串、IN查询、数组(PostgreSQL的数组)、字典(PostgreSQL HStore)等等。

In查询

var t1 = fsql.Select<T>()
  .Where(a => new[] { 1, 2, 3 }.Contains(a.Id))
  .ToSql();
//SELECT .. FROM ..
//WHERE (a.`Id` in (1,2,3))

已优化,防止 where in 元素多过的 SQL 错误

原来:where id in (1..1333)

现在:where id in (1..500) or id in (501..1000) or id in (1001..1333)

In 只能实现单列查询,多列怎么办?

//元组集合
vae lst = new List<(Guid, DateTime)>();

lst.Add((Guid.NewGuid(), DateTime.Now));
lst.Add((Guid.NewGuid(), DateTime.Now));
lst.Add((Guid.NewGuid(), DateTime.Now));
var t2 = fsql.Select<T>()
  .Where(a => lst.Contains(a.Id, a.ct1))
  .ToSql();
//SELECT .. FROM ..
//WHERE (a."Id" = '685ee1f6-bdf6-4719-a291-c709b8a1378f' AND a."ct1" = '2019-12-07 23:55:27' OR 
//a."Id" = '5ecd838a-06a0-4c81-be43-1e77633b7404' AND a."ct1" = '2019-12-07 23:55:27' OR 
//a."Id" = 'b8b366f3-1c03-4547-9c96-d362dd5cae6a' AND a."ct1" = '2019-12-07 23:55:27')

查找今天创建的数据

var t3 = fsql.Select<T>().Where(a => a.CreateTime.Date == DateTime.Today).ToSql();
//这行代码说明 FreeSql 表达式解析强大,不是所有 ORM 都支持

var t4 = fsql.Select<T>().Where(a => a.CreateTime.Between(DateTime.Today, DateTime.Today.AddDays(1))).ToSql();

SqlServer nvarchar/varchar 已兼容表达式解析,分别解析为:N'' 和 '',优化索引执行计划;

自定义表达式函数(v0.11.23)

[ExpressionCall]
public static class DbFunc
{
    //必要定义 static + ThreadLocal
    static ThreadLocal<ExpressionCallContext> context = new ThreadLocal<ExpressionCallContext>();

    public static DateTime FormatDateTime(this DateTime that, string arg1)
    {
        var up = context.Value;
        if (up.DataType == FreeSql.DataType.Sqlite) //重写内容
            context.Value.Result = $"date_format({up.Values["that"]}, {up.Values["arg1"]})";
        return that;
    }
    
    public static string SetDbParameter(this string that, int size)
    {
        if (context.Value.DbParameter != null)
        {
            //已经参数化了,直接修改长度
            //提示:此条件可能开启了全局表达式参数化功能 UseGenerateCommandParameterWithLambda(true)
            context.Value.DbParameter.Size = size;
            return that;
        }
        var guid = Guid.NewGuid().ToString("N").ToLower();
        context.Value.UserParameters.Add(new SqlParameter
        {
            ParameterName = guid,
            SqlDbType = System.Data.SqlDbType.VarChar,
            Size = size,
            Value = that
        });
        return $"@{guid}"; //重写内容
    }
}

var sql1 = fsql.Select<SysModule>()
    .ToSql(a => a.CreateTime.FormatDateTime("yyyy-MM-dd"));
//SELECT date_format(a."CreateTime", 'yyyy-MM-dd') as1 
//FROM "SysModule" a

var sql2 = fsql.Select<SysModule>()
    .Where(a => a.Title == "123123".SetDbParameter(20))
    .ToSql();
//SELECT ...
//FROM [SysModule] a 
//WHERE (a.[Title] = @6a8b79d7001540369a2f52ecbba15679)

[ExpressionCall] 特性可在静态扩展类上标记,也可以在单个静态方法上标记;

ExpressionCallContext 属性 类型 描述
DataType FreeSql.DataType 用于实现不同数据库的适配判断条件
ParsedContent Dictionary<string, string> 函数的各参数解析结果
DbParameter DbParameter that 被参数化的对象(有可能为 null)
UserParameters List<DbParameter> 可附加参数化对象
Result string 返回表达式函数表示的 SQL 字符串

当扩展方法返回值为 string 时,其返回值也可以当作 context.Value.Result 功能

命令参数化(v0.12.1)

在之前 Where(lambda) 解析出来的是纯文本,做了防止注入功能,对数据库执行计划要求高的,现在可以开启 lambda 参数化功能。

var fsql = new FreeSqlBuilder()
    .UseGenerateCommandParameterWithLambda(true)
    ...

var id = 1;
fsql.Select<Song>().Where(a => a.Id == id).ToList();
//SELECT .. FROM `Song` a WHERE `Id` = ?exp_0

生成的参数对象,DbType、Size、Precision、Scale 值设置默认已作优化,与实体属性定义一致。

诡异操作:

如果不希望 string 参数与实体属性的 Size 相同,可利用自定义表达式函数功能,如下:

var name = "testname";
fsql.Select<TestMySqlStringIsNullable>()
    .Where(a => a.varchar == name).ToList();

fsql.Select<TestMySqlStringIsNullable>()
    .Where(a => a.varchar == name.SetDbParameter(10)).ToList();

public class TestMySqlStringIsNullable
{
    public Guid id { get; set; }

    [Column(DbType = "varchar(100)")]
    public string varchar { get; set; }
}

[ExpressionCall]
public static class DbFunc
{
    static ThreadLocal<ExpressionCallContext> context = new ThreadLocal<ExpressionCallContext>();

    public static string SetDbParameter(this string that, int size)
    {
        if (context.Value.DbParameter != null)
            context.Value.DbParameter.Size = size;
        return context.Value.ParsedContent["that"];
    }
}

第一条语句产生的参数对象 Size 为 100,第二条为 10:

image

AOP拦截解析

IFreeSql 对象有 Aop 成员,那里提供一堆 AOP 拦截的方法。其实有一个事件名称:ParseExpression。

/// <summary>
/// 可自定义解析表达式
/// </summary>
EventHandler<AopParseExpressionEventArgs> ParseExpression { get; set; }

public class AopParseExpressionEventArgs : EventArgs {
    public AopParseExpressionEventArgs(Expression expression, Func<Expression, string> freeParse) {
        this.Expression = expression;
        this.FreeParse = freeParse;
    }

    /// <summary>
    /// 内置解析功能,可辅助您进行解析
    /// </summary>
    public Func<Expression, string> FreeParse { get; }

    /// <summary>
    /// 需要您解析的表达式
    /// </summary>
    public Expression Expression { get; }
    /// <summary>
    /// 解析后的内容
    /// </summary>
    public string Result { get; set; }
}

FreeParse 是提供给外部的解析工具,它拥有 FreeSql 所有表达式功能,当您自定义解析的过程中遇到特别难处理的,可通过它快速解析出表达式的子部分内容。

表达式函数全览

表达式 MySql SqlServer PostgreSQL Oracle 功能说明
a ? b : c case when a then b else c end case when a then b else c end case when a then b else c end case when a then b else c end a成立时取b值,否则取c值
a ?? b ifnull(a, b) isnull(a, b) coalesce(a, b) nvl(a, b) 当a为null时,取b值
数字 + 数字 a + b a + b a + b a + b 数字相加
数字 + 字符串 concat(a, b) cast(a as varchar) + cast(b as varchar) case(a as varchar)|| b a|| b 字符串相加,a或b任意一个为字符串时
a - b a - b a - b a - b a - b
a * b a * b a * b a * b a * b
a / b a / b a / b a / b a / b
a / b a div b a / b a / b trunc(a / b) 整除(a,b都为整数)
a % b a % b a % b a % b mod(a,b)

等等...

数组

表达式 MySql SqlServer PostgreSQL Oracle 功能说明
a.Length - - case when a is null then 0 else array_length(a,1) end - 数组长度
常量数组.Length - - array_length(array[常量数组元素逗号分割],1) - 数组长度
a.Any() - - case when a is null then 0 else array_length(a,1) end > 0 - 数组是否为空
常量数组.Contains(b) b in (常量数组元素逗号分割) b in (常量数组元素逗号分割) b in (常量数组元素逗号分割) b in (常量数组元素逗号分割) IN查询
a.Contains(b) - - a @> array[b] - a数组是否包含b元素
a.Concat(b) - - a || b - 数组相连
a.Count() - - 同 Length - 数组长度

一个细节证明 FreeSql 匠心制作

通用的 in 查询 select.Where(a => new []{ 1,2,3 }.Contains(a.xxx))

假设 xxxs 是 pgsql 的数组字段类型,其实会与上面的 in 查询起冲突,FreeSql 解决了这个矛盾 select.Where(a => a.xxxs.Contains(1))

字典 Dictionary<string, string>

表达式 MySql SqlServer PostgreSQL Oracle 功能说明
a.Count - - case when a is null then 0 else array_length(akeys(a),1) end - 字典长度
a.Keys - - akeys(a) - 返回字典所有key数组
a.Values - - avals(a) - 返回字典所有value数组
a.Contains(b) - - a @> b - 字典是否包含b
a.ContainsKey(b) - - a? b - 字典是否包含key
a.Concat(b) - - a || b - 字典相连
a.Count() - - 同 Count - 字典长度

JSON JToken/JObject/JArray

表达式 MySql SqlServer PostgreSQL Oracle 功能说明
a.Count - - jsonb_array_length(coalesce(a, '[])) - json数组类型的长度
a.Any() - - jsonb_array_length(coalesce(a, '[])) > 0 - json数组类型,是否为空
a.Contains(b) - - coalesce(a, '{}') @> b::jsonb - json中是否包含b
a.ContainsKey(b) - - coalesce(a, '{}') ? b - json中是否包含键b
a.Concat(b) - - coalesce(a, '{}') b::jsonb
Parse(a) - - a::jsonb - 转化字符串为json类型

字符串

表达式 MySql SqlServer PostgreSQL Oracle Sqlite
string.Empty '' '' '' ''
string.IsNullOrEmpty(a) (a is null or a = '') (a is null or a = '') (a is null or a = '') (a is null or a = '') (a is null or a = '')
string.Concat(a,b,c...) concat(a, b, c) a + b + c a || b || c a || b || c a || b || c
a.CompareTo(b) strcmp(a, b) - case when a = b then 0 when a > b then 1 else -1 end case when a = b then 0 when a > b then 1 else -1 end case when a = b then 0 when a > b then 1 else -1 end
a.Contains('b') a like '%b%' a like '%b%' a ilike'%b%' a like '%b%' a like '%b%'
a.EndsWith('b') a like '%b' a like '%b' a ilike'%b' a like '%b' a like '%b'
a.IndexOf(b) locate(a, b) - 1 locate(a, b) - 1 strpos(a, b) - 1 instr(a, b, 1, 1) - 1 instr(a, b) - 1
a.Length char_length(a) len(a) char_length(a) length(a) length(a)
a.PadLeft(b, c) lpad(a, b, c) - lpad(a, b, c) lpad(a, b, c) lpad(a, b, c)
a.PadRight(b, c) rpad(a, b, c) - rpad(a, b, c) rpad(a, b, c) rpad(a, b, c)
a.Replace(b, c) replace(a, b, c) replace(a, b, c) replace(a, b, c) replace(a, b, c) replace(a, b, c)
a.StartsWith('b') a like 'b%' a like 'b%' a ilike'b%' a like 'b%' a like 'b%'
a.Substring(b, c) substr(a, b, c + 1) substring(a, b, c + 1) substr(a, b, c + 1) substr(a, b, c + 1) substr(a, b, c + 1)
a.ToLower lower(a) lower(a) lower(a) lower(a) lower(a)
a.ToUpper upper(a) upper(a) upper(a) upper(a) upper(a)
a.Trim trim(a) trim(a) trim(a) trim(a) trim(a)
a.TrimEnd rtrim(a) rtrim(a) rtrim(a) rtrim(a) rtrim(a)
a.TrimStart ltrim(a) ltrim(a) ltrim(a) ltrim(a) ltrim(a)

使用字符串函数可能会出现性能瓶颈,虽然不推荐使用,但是作为功能库这也是不可缺少的功能之一。

日期

表达式 MySql SqlServer PostgreSQL Oracle
DateTime.Now now() getdate() current_timestamp systimestamp
DateTime.UtcNow utc_timestamp() getutcdate() (current_timestamp at time zone 'UTC') sys_extract_utc(systimestamp)
DateTime.Today curdate convert(char(10),getdate(),120) current_date trunc(systimestamp)
DateTime.MaxValue cast('9999/12/31 23:59:59' as datetime) '9999/12/31 23:59:59' '9999/12/31 23:59:59'::timestamp to_timestamp('9999-12-31 23:59:59','YYYY-MM-DD HH24:MI:SS.FF6')
DateTime.MinValue cast('0001/1/1 0:00:00' as datetime) '1753/1/1 0:00:00' '0001/1/1 0:00:00'::timestamp to_timestamp('0001-01-01 00:00:00','YYYY-MM-DD HH24:MI:SS.FF6')
DateTime.Compare(a, b) a - b a - b extract(epoch from a::timestamp-b::timestamp) extract(day from (a-b))
DateTime.DaysInMonth(a, b) dayofmonth(last_day(concat(a, '-', b, '-1'))) datepart(day, dateadd(day, -1, dateadd(month, 1, cast(a as varchar) + '-' + cast(b as varchar) + '-1'))) extract(day from (a
DateTime.Equals(a, b) a = b a = b a = b a = b
DateTime.IsLeapYear(a) a%4=0 and a%100<>0 or a%400=0 a%4=0 and a%100<>0 or a%400=0 a%4=0 and a%100<>0 or a%400=0 mod(a,4)=0 AND mod(a,100)<>0 OR mod(a,400)=0
DateTime.Parse(a) cast(a as datetime) cast(a as datetime) a::timestamp to_timestamp(a,'YYYY-MM-DD HH24:MI:SS.FF6')
a.Add(b) date_add(a, interval b microsecond) dateadd(millisecond, b / 1000, a) a::timestamp+(b
a.AddDays(b) date_add(a, interval b day) dateadd(day, b, a) a::timestamp+(b
a.AddHours(b) date_add(a, interval b hour) dateadd(hour, b, a) a::timestamp+(b
a.AddMilliseconds(b) date_add(a, interval b*1000 microsecond) dateadd(millisecond, b, a) a::timestamp+(b
a.AddMinutes(b) date_add(a, interval b minute) dateadd(minute, b, a) a::timestamp+(b
a.AddMonths(b) date_add(a, interval b month) dateadd(month, b, a) a::timestamp+(b
a.AddSeconds(b) date_add(a, interval b second) dateadd(second, b, a) a::timestamp+(b
a.AddTicks(b) date_add(a, interval b/10 microsecond) dateadd(millisecond, b / 10000, a) a::timestamp+(b
a.AddYears(b) date_add(a, interval b year) dateadd(year, b, a) a::timestamp+(b
a.Date cast(date_format(a, '%Y-%m-%d') as datetime) convert(char(10),a,120) a::date trunc(a)
a.Day dayofmonth(a) datepart(day, a) extract(day from a::timestamp) cast(to_char(a,'DD') as number)
a.DayOfWeek dayofweek(a) datepart(weekday, a) - 1 extract(dow from a::timestamp) case when to_char(a)='7' then 0 else cast(to_char(a) as number) end
a.DayOfYear dayofyear(a) datepart(dayofyear, a) extract(doy from a::timestamp) cast(to_char(a,'DDD') as number)
a.Hour hour(a) datepart(hour, a) extract(hour from a::timestamp) cast(to_char(a,'HH24') as number)
a.Millisecond floor(microsecond(a) / 1000) datepart(millisecond, a) extract(milliseconds from a::timestamp)-extract(second from a::timestamp)*1000 cast(to_char(a,'FF3') as number)
a.Minute minute(a) datepart(minute, a) extract(minute from a::timestamp) cast(to_char(a,'MI') as number)
a.Month month(a) datepart(month, a) extract(month from a::timestamp) cast(to_char(a,'FF3') as number)
a.Second second(a) datepart(second, a) extract(second from a::timestamp) cast(to_char(a,'SS') as number)
a.Subtract(b) timestampdiff(microsecond, b, a) datediff(millisecond, b, a) * 1000 (extract(epoch from a::timestamp-b::timestamp)*1000000) a - b
a.Ticks timestampdiff(microsecond, '0001-1-1', a) * 10 datediff(millisecond, '1970-1-1', a) * 10000 + 621355968000000000 extract(epoch from a::timestamp)*10000000+621355968000000000 cast(to_char(a,'FF7') as number)
a.TimeOfDay timestampdiff(microsecond, date_format(a, '%Y-%m-%d'), a) '1970-1-1 ' + convert(varchar, a, 14) extract(epoch from a::time)*1000000 a - trunc(a)
a.Year year(a) datepart(year, a) extract(year from a::timestamp)
a.Equals(b) a = b a = b a = b a = b
a.CompareTo(b) a - b a - b a - b a - b
a.ToString() date_format(a, '%Y-%m-%d %H:%i:%s.%f') convert(varchar, a, 121) to_char(a, 'YYYY-MM-DD HH24:MI:SS.US') to_char(a,'YYYY-MM-DD HH24:MI:SS.FF6')

时间

表达式 MySql(微秒) SqlServer(秒) PostgreSQL(微秒) Oracle(Interval day(9) to second(7))
TimeSpan.Zero 0 0 - 0微秒
TimeSpan.MaxValue 922337203685477580 922337203685477580 - numtodsinterval(233720368.5477580,'second')
TimeSpan.MinValue -922337203685477580 -922337203685477580 - numtodsinterval(-233720368.5477580,'second')
TimeSpan.Compare(a, b) a - b a - b - extract(day from (a-b))
TimeSpan.Equals(a, b) a = b a = b - a = b
TimeSpan.FromDays(a) a * 1000000 * 60 * 60 * 24 a * 1000000 * 60 * 60 * 24 - numtodsinterval(a*86400,'second')
TimeSpan.FromHours(a) a * 1000000 * 60 * 60 a * 1000000 * 60 * 60 - numtodsinterval(a*3600,'second')
TimeSpan.FromMilliseconds(a) a * 1000 a * 1000 - numtodsinterval(a/1000,'second')
TimeSpan.FromMinutes(a) a * 1000000 * 60 a * 1000000 * 60 - numtodsinterval(a*60,'second')
TimeSpan.FromSeconds(a) a * 1000000 a * 1000000 - numtodsinterval(a,'second')
TimeSpan.FromTicks(a) a / 10 a / 10 - numtodsinterval(a/10000000,'second')
a.Add(b) a + b a + b - a + b
a.Subtract(b) a - b a - b - a - b
a.CompareTo(b) a - b a - b - extract(day from (a-b))
a.Days a div (1000000 * 60 * 60 * 24) a div (1000000 * 60 * 60 * 24) - extract(day from a)
a.Hours a div (1000000 * 60 * 60) mod 24 a div (1000000 * 60 * 60) mod 24 - extract(hour from a)
a.Milliseconds a div 1000 mod 1000 a div 1000 mod 1000 - cast(substr(extract(second from a)-floor(extract(second from a)),2,3) as number)
a.Seconds a div 1000000 mod 60 a div 1000000 mod 60 - extract(second from a)
a.Ticks a * 10 a * 10 - (extract(day from a)*86400+extract(hour from a)*3600+extract(minute from a)*60+extract(second from a))*10000000
a.TotalDays a / (1000000 * 60 * 60 * 24) a / (1000000 * 60 * 60 * 24) - extract(day from a)
a.TotalHours a / (1000000 * 60 * 60) a / (1000000 * 60 * 60) - (extract(day from a)*24+extract(hour from a))
a.TotalMilliseconds a / 1000 a / 1000 - (extract(day from a)*86400+extract(hour from a)*3600+extract(minute from a)*60+extract(second from a))*1000
a.TotalMinutes a / (1000000 * 60) a / (1000000 * 60) -
a.TotalSeconds a / 1000000 a / 1000000 - (extract(day from a)*86400+extract(hour from a)*3600+extract(minute from a)*60+extract(second from a))
a.Equals(b) a = b a = b - a = b
a.ToString() cast(a as varchar) cast(a as varchar) - to_char(a)

数学函数

表达式 MySql SqlServer PostgreSQL Oracle
Math.Abs(a) abs(a) abs(a) abs(a)
Math.Acos(a) acos(a) acos(a) acos(a) acos(a)
Math.Asin(a) asin(a) asin(a) asin(a) asin(a)
Math.Atan(a) atan(a) atan(a) atan(a) atan(a)
Math.Atan2(a, b) atan2(a, b) atan2(a, b) atan2(a, b) -
Math.Ceiling(a) ceiling(a) ceiling(a) ceiling(a) ceil(a)
Math.Cos(a) cos(a) cos(a) cos(a) cos(a)
Math.Exp(a) exp(a) exp(a) exp(a) exp(a)
Math.Floor(a) floor(a) floor(a) floor(a) floor(a)
Math.Log(a) log(a) log(a) log(a) log(e,a)
Math.Log10(a) log10(a) log10(a) log10(a) log(10,a)
Math.PI(a) 3.1415926535897931 3.1415926535897931 3.1415926535897931 3.1415926535897931
Math.Pow(a, b) pow(a, b) power(a, b) pow(a, b) power(a, b)
Math.Round(a, b) round(a, b) round(a, b) round(a, b) round(a, b)
Math.Sign(a) sign(a) sign(a) sign(a) sign(a)
Math.Sin(a) sin(a) sin(a) sin(a) sin(a)
Math.Sqrt(a) sqrt(a) sqrt(a) sqrt(a) sqrt(a)
Math.Tan(a) tan(a) tan(a) tan(a) tan(a)
Math.Truncate(a) truncate(a, 0) floor(a) trunc(a, 0) trunc(a, 0)

类型转换

表达式 MySql SqlServer PostgreSQL Oracle Sqlite
Convert.ToBoolean(a) | bool.Parse(a) a not in ('0','false') a not in ('0','false') a::varchar not in ('0','false','f','no') - a not in ('0','false')
Convert.ToByte(a) | byte.Parse(a) cast(a as unsigned) cast(a as tinyint) a::int2 cast(a as number) cast(a as int2)
Convert.ToChar(a) substr(cast(a as char),1,1) substring(cast(a as nvarchar),1,1) substr(a::char,1,1) substr(to_char(a),1,1) substr(cast(a as character),1,1)
Convert.ToDateTime(a) | DateTime.Parse(a) cast(a as datetime) cast(a as datetime) a::timestamp to_timestamp(a,'YYYY-MM-DD HH24:MI:SS.FF6') datetime(a)
Convert.ToDecimal(a) | decimal.Parse(a) cast(a as decimal(36,18)) cast(a as decimal(36,19)) a::numeric cast(a as number) cast(a as decimal(36,18))
Convert.ToDouble(a) | double.Parse(a) cast(a as decimal(32,16)) cast(a as decimal(32,16)) a::float8 cast(a as number) cast(a as double)
Convert.ToInt16(a) | short.Parse(a) cast(a as signed) cast(a as smallint) a::int2 cast(a as number) cast(a as smallint)
Convert.ToInt32(a) | int.Parse(a) cast(a as signed) cast(a as int) a::int4 cast(a as number) cast(a as smallint)
Convert.ToInt64(a) | long.Parse(a) cast(a as signed) cast(a as bigint) a::int8 cast(a as number) cast(a as smallint)
Convert.ToSByte(a) | sbyte.Parse(a) cast(a as signed) cast(a as tinyint) a::int2 cast(a as number) cast(a as smallint)
Convert.ToSingle(a) | float.Parse(a) cast(a as decimal(14,7)) cast(a as decimal(14,7)) a::float4 cast(a as number) cast(a as float)
Convert.ToString(a) cast(a as char) cast(a as nvarchar) a::varchar to_char(a) cast(a as character)
Convert.ToUInt16(a) | ushort.Parse(a) cast(a as unsigned) cast(a as smallint) a::int2 cast(a as number) cast(a as unsigned)
Convert.ToUInt32(a) | uint.Parse(a) cast(a as unsigned) cast(a as int) a::int4 cast(a as number) cast(a as decimal(10,0))
Convert.ToUInt64(a) | ulong.Parse(a) cast(a as unsigned) cast(a as bigint) a::int8 cast(a as number) cast(a as decimal(21,0))
Guid.Parse(a) substr(cast(a as char),1,36) cast(a as uniqueidentifier) a::uuid substr(to_char(a),1,36) substr(cast(a as character),1,36)
Guid.NewGuid() - newid() - - -
new Random().NextDouble() rand() rand() random() dbms_random.value random()

参考资料

You can’t perform that action at this time.