PostgreSQL是一种开源的关系型数据库管理系统,具有强大的功能和可扩展性。在PostgreSQL中,to_date和extract是两个常用的函数,可以结合使用来进行日期和时间的处理。 to_date函数:to_date函数用于将字符串转换为日期类型。它的语法如下: to_date(string, format) string:要转换的字符串。
current_date);/* show the beginning of the first day of the week */SELECTdate_trunc('week',current_date);/* show the beginning of the first day of the year */SELECTdate_trunc('year',current_date);/* show the beginning of the first day of the current quarter */SELECTdate_trunc('q...
cqdb=# prepare bar(date) as select extract (year from date $1); ERROR: syntax error at or near "$1" LINE 1: prepare bar(date) as select extract (year from date $1); ^ cqdb=# prepare baz(date) as select extract (year from $1); PREPARE cqdb=# --- Maciek Sakrejda | System...
The PostgreSQL EXTRACT() function is used to retrieves subfields such as year or hour from date/time values. The source must be a value expression of type timestamp, time, or interval. The field is an identifier or string that selects what field to be extracted from the source value. Th...
yearYear as 4-digits Note See also thedate_part function. Applies To The extract function can be used in the following versions of PostgreSQL: PostgreSQL 9.4, PostgreSQL 9.3, PostgreSQL 9.2, PostgreSQL 9.1, PostgreSQL 9.0, PostgreSQL 8.4
SELECT c.customer_id, c.customer_name FROM customers c WHERE EXISTS ( SELECT 1 FROM orders o WHERE o.customer_id = c.customer_id AND EXTRACT(YEAR FROM o.order_date) = EXTRACT(YEAR FROM SYSDATE) - 1 ); 在这个例子中,EXTRACT函数用于确定订单日期是否在过去一年内,而EXISTS子句则用于检查...
SELECT EXTRACT(YEAR FROM CURRENT_DATE) AS year; Here, the query above should return the year as ‘2022’ as shown: year --- 2022 NOTE: The extract() method is part of standard SQL and is supported by major database engines such as MySQL, PostgreSQL, and Oracle. However...
Write a MySQL query to extract the year from the current date. Code: -- This SQL query extracts the year component from the current date and time.SELECTEXTRACT(YEARFROMNOW()); Copy Explanation: The EXTRACT() function is used to extract a specific component (in this case, ...
SQL Date Functions > EXTRACT Function The EXTRACT function is used to retrieve a specific component of a date or a timestamp. This function is available in several databases such as MySQL, Oracle, DB2, PostgreSQL, and Google BigQuery. Note that this function is not available in SQL Server ...
EXTRACT(unit FROM date) 是一个标准 SQL 函数,用于从日期或日期时间表达式中提取指定的时间单位(如年、月、日、小时等)。它在数据分析、报告生成、时间序...