FreeSql/Docs/expression.md

表达式函数

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	减
a * b	a * b	a * b	a * b	a * b	乘
a / b	a / b	a / b	a / b	a / b	除
a % b	a % b	a % b	a % b	mod(a,b)	模

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

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

字符串对象

表达式	MySql	SqlServer	PostgreSQL	Oracle	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 = '')	(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	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 like '%b%'	a是否包含b
a.EndsWith('b')	a like '%b'	a like '%b'	a ilike'%b'	a like '%b'	a尾部是否包含b
a.IndexOf(b)	locate(a, b) - 1	locate(a, b) - 1	strpos(a, b) - 1	instr(a, b, 1, 1) - 1	查找a中出现b的位置
a.Length	char_length(a)	len(a)	char_length(a)	length(a)	返回a的字符串长度
a.PadLeft(b, c)	lpad(a, 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)	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)	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 like '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)	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)	lower(a)	转小写
a.ToUpper	upper(a)	upper(a)	upper(a)	upper(a)	转大写
a.Trim	trim(a)	trim(a)	trim(a)	trim(a)	移除两边字符
a.TrimEnd	rtrim(a)	rtrim(a)	rtrim(a)	rtrim(a)	移除左侧指定字符
a.TrimStart	ltrim(a)	ltrim(a)	ltrim(a)	ltrim(a)	移除右侧指定字符

日期对象

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)	年
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')

时间对象

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
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	cast(a as number)
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)
Convert.ToDateTime(a)	cast(a as datetime)	cast(a as datetime)	a::timestamp	to_timestamp(a,'YYYY-MM-DD HH24:MI:SS.FF6')
Convert.ToDecimal(a)	cast(a as decimal(36,18))	cast(a as decimal(36,19))	a::numeric	cast(a as number)
Convert.ToDouble(a)	cast(a as decimal(32,16))	cast(a as decimal(32,16))	a::float8	cast(a as number)
Convert.ToInt16(a)	cast(a as signed)	cast(a as smallint)	a::int2	cast(a as number)
Convert.ToInt32(a)	cast(a as signed)	cast(a as int)	a::int4	cast(a as number)
Convert.ToInt64(a)	cast(a as signed)	cast(a as bigint)	a::int8	cast(a as number)
Convert.ToSByte(a)	cast(a as signed)	cast(a as tinyint)	a::int2	cast(a as number)
Convert.ToString(a)	cast(a as decimal(14,7))	cast(a as decimal(14,7))	a::float4	to_char(a)
Convert.ToSingle(a)	cast(a as char)	cast(a as nvarchar)	a::varchar	cast(a as number)
Convert.ToUInt16(a)	cast(a as unsigned)	cast(a as smallint)	a::int2	cast(a as number)
Convert.ToUInt32(a)	cast(a as unsigned)	cast(a as int)	a::int4	cast(a as number)
Convert.ToUInt64(a)	cast(a as unsigned)	cast(a as bigint)	a::int8	cast(a as number)