FreeSql/Docs/expression.md

表达式函数

表达式	MySql	SqlServer	PostgreSQL	功能说明
a ? b : c	case when athen b else c end	case when athen b else c end	case when athen 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)	当a为null时，取b值
数字 + 数字	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	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	减
a * b	a * b	a * b	a * b	乘
a / b	a / b	a / b	a / b	乘
a % b	a % b	a % b	a % b	模

等等...

数组

表达式	MySql	SqlServer	PostgreSQL	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)	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

字典 Dictionary<string, string>

表达式	MySql	SqlServer	PostgreSQL	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	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, '{}')
Parse(a)	-	-	a::jsonb	转化字符串为json类型

字符串对象

表达式	MySql	SqlServer	PostgreSQL	功能说明
string.Empty	''	''	''	空字符串表示
string.IsNullOrEmpty(a)	(a is null or a = '')	(a is null or a = '')	(a is null or a = '')	空字符串表示
a.CompareTo(b)	strcmp(a, b)	-	case when a = b then 0 when a > b then 1 else -1 end	比较a和b大小
a.Contains('b')	a like '%b%'	a like '%b%'	a ilike'%b%'	a是否包含b
a.EndsWith('b')	a like '%b'	a like '%b'	a ilike'%b'	a尾部是否包含b
a.IndexOf(b)	locate(a, b) - 1	locate(a, b) - 1	strpos(a, b) - 1	查找a中出现b的位置
a.Length	char_length(a)	len(a)	char_length(a)	返回a的字符串长度
a.PadLeft(b, c)	lpad(a, b, c)	-	lpad(a, b, c)	在a的左侧充字符c，直到字符串长度大于b
a.PadRight(b, c)	rpad(a, b, c)	-	rpad(a, b, c)	在a的右侧充字符c，直到字符串长度大于b
a.Replace(b, c)	replace(a, b, c)	replace(a, b, c)	replace(a, b, c)	将a中字符串b，替换成c
a.StartsWith('b')	a like 'b%'	a like 'b%'	a ilike'b%'	a头部是否包含b
a.Substring(b, c)	substr(a, b, c + 1)	substring(a, b, c + 1)	substr(a, b, c + 1)	截取a中位置b到c的内容
a.ToLower	lower(a)	lower(a)	lower(a)	转小写
a.ToUpper	upper(a)	upper(a)	upper(a)	转大写
a.Trim	trim(a)	trim(a)	trim(a)	移除两边字符
a.TrimEnd	rtrim(a)	rtrim(a)	rtrim(a)	移除左侧指定字符
a.TrimStart	ltrim(a)	ltrim(a)	ltrim(a)	移除右侧指定字符

日期对象

表达式	MySql	SqlServer	PostgreSQL	功能说明
DateTime.Now	now()	getdate()	current_timestamp	取本地时间
DateTime.UtcNow	utc_timestamp()	getutcdate()	(current_timestamp at time zone 'UTC')	取UTC时间
DateTime.Today	curdate	convert(char(10),getdate(),120)	current_date	取本地时间，日期部分
DateTime.MaxValue	cast('9999/12/31 23:59:59' as datetime)	'1753/1/1 0:00:00'	'0001/1/1 0:00:00'::timestamp	最大时间
DateTime.MinValue	cast('0001/1/1 0:00:00' as datetime)	'9999/12/31 23:59:59'	'9999/12/31 23:59:59'::timestamp	最小时间
DateTime.Compare(a, b)	a - b	a - b	extract(epoch from a::timestamp-b::timestamp)	比较a和b的大小
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	比较a和b相等
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	判断闰年
DateTime.Parse(a)	cast(a as datetime)	cast(a as datetime)	a::timestamp	转换日期类型
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	获取a的日期部分
a.Day	dayofmonth(a)	datepart(day, a)	extract(day from a::timestamp)	获取a在月的第几天
a.DayOfWeek	dayofweek(a)	datepart(weekday, a) - 1	extract(dow from a::timestamp)	获取a在周的第几天
a.DayOfYear	dayofyear(a)	datepart(dayofyear, a)	extract(doy from a::timestamp)	获取a在年的第几天
a.Hour	hour(a)	datepart(hour, a)	extract(hour from a::timestamp)	小时
a.Millisecond	floor(microsecond(a) / 1000)	datepart(millisecond, a)	extract(milliseconds from a::timestamp)-extract(second from a::timestamp)*1000	毫秒
a.Minute	minute(a)	datepart(minute, a)	extract(minute from a::timestamp)	分钟
a.Month	month(a)	datepart(month, a)	extract(month from a::timestamp)	月
a.Second	second(a)	datepart(second, a)	extract(second from a::timestamp)	秒
a.Subtract(b)	timestampdiff(microsecond, b, a)	datediff(millisecond, b, a) * 1000	(extract(epoch from a::timestamp-b::timestamp)*1000000)	将a的值和b相减
a.Ticks	timestampdiff(microsecond, '0001-1-1', a) * 10	datediff(millisecond, '1970-1-1', a) * 10000 + 621355968000000000	extract(epoch from a::timestamp)*10000000+621355968000000000	刻度总数
a.TimeOfDay	timestampdiff(microsecond, date_format(a, '%Y-%m-%d'), a)	'1970-1-1 ' + convert(varchar, a, 14)	extract(epoch from a::time)*1000000	获取a的时间部分
a.Year	year(a)	datepart(year, a)	extract(year from a::timestamp)	年
a.Equals(b)	a = b	a = b	a = b	比较a和b相等
a.CompareTo(b)	a - b	a - b	a - b	比较a和b大小
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')	转换字符串

时间对象

表达式	MySql(微秒)	SqlServer(秒)	PostgreSQL(微秒)	功能说明
TimeSpan.Zero	0	0	-	0微秒
TimeSpan.MaxValue	922337203685477580	922337203685477580	-	最大微秒时间
TimeSpan.MinValue	-922337203685477580	-922337203685477580	-	最小微秒时间
TimeSpan.Compare(a, b)	a - b	a - b	-	比较a和b的大小
TimeSpan.Equals(a, b)	a = b	a = b	-	比较a和b相等
TimeSpan.FromDays(a)	a * 1000000 * 60 * 60 * 24	a * 1000000 * 60 * 60 * 24	-	a天的微秒值
TimeSpan.FromHours(a)	a * 1000000 * 60 * 60	a * 1000000 * 60 * 60	-	a小时的微秒值
TimeSpan.FromMilliseconds(a)	a * 1000	a * 1000	-	a毫秒的微秒值
TimeSpan.FromMinutes(a)	a * 1000000 * 60	a * 1000000 * 60	-	a分钟的微秒值
TimeSpan.FromSeconds(a)	a * 1000000	a * 1000000	-	a秒钟的微秒值
TimeSpan.FromTicks(a)	a / 10	a / 10	-	a刻度的毫秒值
a.Add(b)	a + b	a + b	-	增加值
a.Subtract(b)	a - b	a - b	-	将a的值和b相减
a.CompareTo(b)	a - b	a - b	-	比较a和b大小
a.Days	a div (1000000 * 60 * 60 * 24)	a div (1000000 * 60 * 60 * 24)	-	天数部分
a.Hours	a div (1000000 * 60 * 60) mod 24	a div (1000000 * 60 * 60) mod 24	-	小时部分
a.Milliseconds	a div 1000 mod 1000	a div 1000 mod 1000	-	毫秒部分
a.Seconds	a div 1000000 mod 60	a div 1000000 mod 60	-	秒数部分
a.Ticks	a * 10	a * 10	-	刻度总数
a.TotalDays	a / (1000000 * 60 * 60 * 24)	a / (1000000 * 60 * 60 * 24)	-	总天数(含小数)
a.TotalHours	a / (1000000 * 60 * 60)	a / (1000000 * 60 * 60)	-	总小时(含小数)
a.TotalMilliseconds	a / 1000	a / 1000	-	总毫秒(含小数)
a.TotalMinutes	a / (1000000 * 60)	a / (1000000 * 60)	-	总分钟(含小数)
a.TotalSeconds	a / 1000000	a / 1000000	-	总秒数(含小数)
a.Equals(b)	a = b	a = b	-	比较a和b相等
a.ToString()	cast(a as varchar)	cast(a as varchar)	-	转换字符串

数学函数

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

类型转换

表达式	MySql	SqlServer	PostgreSQL
Convert.ToBoolean(a)	a not in ('0','false')	a not in ('0','false')	a::varchar not in ('0','false','f','no')
Convert.ToByte(a)	cast(a as unsigned)	cast(a as tinyint)	a::int2
Convert.ToChar(a)	substr(cast(a as char),1,1)	substring(cast(a as nvarchar),1,1)	substr(a::char,1,1)
Convert.ToDateTime(a)	cast(a as datetime)	cast(a as datetime)	a::timestamp
Convert.ToDecimal(a)	cast(a as decimal(36,18))	cast(a as decimal(36,19))	a::numeric
Convert.ToDouble(a)	cast(a as decimal(32,16))	cast(a as decimal(32,16))	a::float8
Convert.ToInt16(a)	cast(a as signed)	cast(a as smallint)	a::int2
Convert.ToInt32(a)	cast(a as signed)	cast(a as int)	a::int4
Convert.ToInt64(a)	cast(a as signed)	cast(a as bigint)	a::int8
Convert.ToSByte(a)	cast(a as signed)	cast(a as tinyint)	a::int2
Convert.ToString(a)	cast(a as decimal(14,7))	cast(a as decimal(14,7))	a::float4
Convert.ToSingle(a)	cast(a as char)	cast(a as nvarchar)	a::varchar
Convert.ToUInt16(a)	cast(a as unsigned)	cast(a as smallint)	a::int2
Convert.ToUInt32(a)	cast(a as unsigned)	cast(a as int)	a::int4
Convert.ToUInt64(a)	cast(a as unsigned)	cast(a as bigint)	a::int8