日期时间型:DATE, DATETIME, DATETIME2, TIME 浮点型:FLOAT, REAL, DECIMAL 每种数据类型都有其特定的用途,开发者需要根据业务需求选用合适的数据类型。 4. 过滤和排序数据 使用WHERE子句可以对查询结果进行过滤,使用ORDER BY子句可以对结果进行排序。 sql SELECT * FROM table_name WHERE condition ORDER BY column...
This function collapses a date/time to a fixed interval, eliminating the need to round datetime values, extract date parts, perform wild conversions to and from other types like float, or make elaborate and unintuitive dateadd/datediff calculations (sometimes using magic dates from the past). The...
The T-SQL substring function will allow you to extract characters from a string and requires three parameters: expression, start, and length. Expression is a character, binary, text, ntext, or image expression, while start specifies where you want to start using an integer or bigint expression...
在PostgreSQL中,你可以直接访问timestamp或timestamptz类型列的time部分,或者使用DATE_TRUNC和类型转换来达到类似的效果。不过更直接的方法是使用::time进行转换。 SELECT your_datetime_column::time AS time_part FROM your_table; 或者你也可以使用EXTRACT函数来获取具体的小时、分钟和秒: SELECT EXTRACT(HOUR FROM...
O:select ceil(-1.001) value from dual 3.取整(小) S:select floor(-1.001) value O:select floor(-1.001) value from dual 4.取整(截取) S:select cast(-1.002 as int) value O:select trunc(-1.002) value from dual 5.四舍五入 S:select round(1.23456,4) value 1.23460 ...
Data Types and Operators:SQL supports a wide range of standard data types, such as integers, strings, and dates. T-SQL, however, extends these data types to include proprietary types likeunique identifier(for GUIDs) anddatetime2(for more precise date/time values). Additionally, T-SQL includes...
o:selectlast_day(sysdate) valuefromdual41.本星期的某一天(比如星期日) s:不知道 o:selectnext_day(sysdate,7) vaulefromdual;42.字符串转时间 s:可以直接转或者selectcast('2004-09-08'asdatetime) value o:selectto_date('2004-01-05 22:09:38','yyyy-mm-dd hh24-mi-ss') vaulefromdual;43.求...
Convert SQL datetime to Excel datetime convert sql variant to date Convert sql_variant to nvarchar without rounding Convert string into datetime with timezone Convert String With Int's Comma Seperated Into Acutal Int's With Commas For Use IN Convert text from c# byte array to sq...
CURTIME():This is also the date format function that can give back the current time. EXTRACT():This function can give back a single part or time. DATE_SUB():This function can subtract a particular time interval from a date. DATE_FORMAT():It can present the date or time in various for...
UNIX_TIMESTAMP(date) 示例: 假设有一个名为 orders 的表,其中包含一个名为 order_date 的列,该列的数据类型为 DATETIME。 SELECT UNIX_TIMESTAMP(order_date) AS timestamp FROM orders; 这将返回每个订单日期的时间戳。 2. PostgreSQL 在PostgreSQL中,可以使用 EXTRACT(EPOCH FROM ...) 将日期或时间转换...