Python SQLite3数据库日期与时间常见函数用法分析

import sqlite3#con = sqlite3.connect('example.db')con = sqlite3.connect(":memory:")c = con.cursor()# Create tablec.execute('''CREATE TABLE stocks       (date text, trans text, symbol text, qty real, price real)''')# Insert a row of datac.execute("INSERT INTO stocks VALUES (?,?,?,?,?)", ('2006-03-27','BUY','RHAT',100,60.14))# Larger example that inserts many records at a timepurchases = [('2006-03-28', 'BUY', 'IBM', 1000, 45.00),       ('2006-04-05', 'BUY', 'MSFT', 1000, 72.00),       ('2006-04-06', 'SELL', 'IBM', 500, 53.00),       ('2006-04-07', 'SELL', 'MSFT', 500, 74.00),       ('2006-04-08', 'SELL', 'IBM', 500, 54.00),       ('2006-04-09', 'SELL', 'MSFT', 500, 73.00),       ('2006-04-10', 'SELL', 'MSFT', 500, 75.00),       ('2006-04-12', 'SELL', 'IBM', 500, 55.00),      ]c.executemany('INSERT INTO stocks VALUES (?,?,?,?,?)', purchases)# Save (commit) the changescon.commit()# Do this insteadt = ('RHAT',)c.execute('SELECT * FROM stocks WHERE symbol=?', t)#print(c.fetchone())#for row in c.execute('SELECT * FROM stocks ORDER BY price'):#  print(row)#for row in c.execute('SELECT * FROM stocks LIMIT 5 OFFSET 0'):#  print(row)for row in c.execute('SELECT * FROM stocks LIMIT 5 OFFSET 1'):  print(row)#Select Top N * From# ====================================================================================# SQLite 日期 & 时间# ====================================================================================print('='*30)print('SQLite 日期 & 时间')print('='*30)# 计算当前日期c.execute("SELECT date('now')")print(c.fetchone())# 计算当前月份的最后一天：c.execute("SELECT date('now','start of month','+1 month','-1 day');")print(c.fetchone())# 计算给定 UNIX 时间戳 1092941466 的日期和时间：c.execute("SELECT datetime(1092941466, 'unixepoch');")print(c.fetchone())# 计算给定 UNIX 时间戳 1092941466 相对本地时区的日期和时间：c.execute("SELECT datetime(1092941466, 'unixepoch', 'localtime');")print(c.fetchone())# 计算当前的 UNIX 时间戳：c.execute("SELECT datetime(1092941466, 'unixepoch', 'localtime');")print(c.fetchone())# 计算美国"独立宣言"签署以来的天数：c.execute("SELECT julianday('now') - julianday('1776-07-04');")print(c.fetchone())# 计算从 2004 年某一特定时刻以来的秒数：c.execute("SELECT strftime('%s','now') - strftime('%s','2004-01-01 02:34:56');")print(c.fetchone())# 计算当年 10 月的第一个星期二的日期：c.execute("SELECT date('now','start of year','+9 months','weekday 2');")print(c.fetchone())# 计算从 UNIX 纪元算起的以秒为单位的时间（类似 strftime('%s','now') ，不同的是这里有包括小数部分）：c.execute("SELECT (julianday('now') - 2440587.5)*86400.0;")print(c.fetchone())# 在 UTC 与本地时间值之间进行转换，当格式化日期时，使用 utc 或 localtime 修饰符，如下所示：c.execute("SELECT time('12:00', 'localtime');")print(c.fetchone())#c.execute("SELECT time('12:00', 'utc');")print(c.fetchone())con.close()# ====================================================================================# SQLite 常用函数# ====================================================================================print('='*30)print('SQLite 常用函数')print('='*30)con = sqlite3.connect(":memory:")c = con.cursor()# Create tablec.execute('''CREATE TABLE COMPANY      (ID integer, NAME text, AGE integer, ADDRESS text, SALARY real)''')# Larger example that inserts many records at a timepurchases = [(1,'Paul',32,'California',20000.0),       (2,'Allen',25,'Texas',15000.0),       (3,'Teddy',23,'Norway',20000.0),       (4,'Mark',25,'Rich-Mond',65000.0),       (5,'David',27,'Texas',85000.0),       (6,'Kim',22,'South-Hall',45000.0),       (7,'James',24,'Houston',10000.0)]c.executemany('INSERT INTO COMPANY VALUES (?,?,?,?,?)', purchases)# Save (commit) the changescon.commit()# 返回数据库表最后 n 行记录# 先计算一个数据库表中的行数c.execute("SELECT count(*) FROM COMPANY;")last = c.fetchone()[0]n = 5c.execute("SELECT * FROM COMPANY LIMIT ? OFFSET ?;", (n, last-n))for row in c:  print(row)# 计算一个数据库表中的行数c.execute("SELECT count(*) FROM COMPANY;")print(c.fetchone())# 选择某列的最大值c.execute("SELECT max(salary) FROM COMPANY;")print(c.fetchone())# 选择某列的最小值c.execute("SELECT min(salary) FROM COMPANY;")print(c.fetchone())# 计算某列的平均值c.execute("SELECT avg(salary) FROM COMPANY;")print(c.fetchone())# 为一个数值列计算总和c.execute("SELECT sum(salary) FROM COMPANY;")print(c.fetchone())# 返回一个介于 -9223372036854775808 和 +9223372036854775807 之间的伪随机整数c.execute("SELECT random() AS Random;")print(c.fetchone())# 返回数值参数的绝对值c.execute("SELECT abs(5), abs(-15), abs(NULL), abs(0), abs('ABC');")print(c.fetchone())# 把字符串转换为大写字母c.execute("SELECT upper(name) FROM COMPANY;")print(c.fetchone())# 把字符串转换为小写字母c.execute("SELECT lower(name) FROM COMPANY;")print(c.fetchone())# 返回字符串的长度c.execute("SELECT name, length(name) FROM COMPANY;")print(c.fetchone())# 返回 SQLite 库的版本c.execute("SELECT sqlite_version() AS 'SQLite Version';")print(c.fetchone())#c.execute("SELECT CURRENT_TIMESTAMP;")print(c.fetchone())