Python SQLite3數(shù)據(jù)庫日期與時(shí)間常見函數(shù)用法分析
本文實(shí)例講述了Python SQLite3數(shù)據(jù)庫日期與時(shí)間常見函數(shù)。分享給大家供大家參考,具體如下:
import sqlite3 #con = sqlite3.connect('example.db') con = sqlite3.connect(":memory:") c = con.cursor() # Create table c.execute('''CREATE TABLE stocks (date text, trans text, symbol text, qty real, price real)''') # Insert a row of data c.execute("INSERT INTO stocks VALUES (?,?,?,?,?)", ('2006-03-27','BUY','RHAT',100,60.14)) # Larger example that inserts many records at a time purchases = [('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 changes con.commit() # Do this instead t = ('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 & 時(shí)間 # ==================================================================================== print('='*30) print('SQLite 日期 & 時(shí)間') print('='*30) # 計(jì)算當(dāng)前日期 c.execute("SELECT date('now')") print(c.fetchone()) # 計(jì)算當(dāng)前月份的最后一天: c.execute("SELECT date('now','start of month','+1 month','-1 day');") print(c.fetchone()) # 計(jì)算給定 UNIX 時(shí)間戳 1092941466 的日期和時(shí)間: c.execute("SELECT datetime(1092941466, 'unixepoch');") print(c.fetchone()) # 計(jì)算給定 UNIX 時(shí)間戳 1092941466 相對本地時(shí)區(qū)的日期和時(shí)間: c.execute("SELECT datetime(1092941466, 'unixepoch', 'localtime');") print(c.fetchone()) # 計(jì)算當(dāng)前的 UNIX 時(shí)間戳: c.execute("SELECT datetime(1092941466, 'unixepoch', 'localtime');") print(c.fetchone()) # 計(jì)算美國"獨(dú)立宣言"簽署以來的天數(shù): c.execute("SELECT julianday('now') - julianday('1776-07-04');") print(c.fetchone()) # 計(jì)算從 2004 年某一特定時(shí)刻以來的秒數(shù): c.execute("SELECT strftime('%s','now') - strftime('%s','2004-01-01 02:34:56');") print(c.fetchone()) # 計(jì)算當(dāng)年 10 月的第一個(gè)星期二的日期: c.execute("SELECT date('now','start of year','+9 months','weekday 2');") print(c.fetchone()) # 計(jì)算從 UNIX 紀(jì)元算起的以秒為單位的時(shí)間(類似 strftime('%s','now') ,不同的是這里有包括小數(shù)部分): c.execute("SELECT (julianday('now') - 2440587.5)*86400.0;") print(c.fetchone()) # 在 UTC 與本地時(shí)間值之間進(jìn)行轉(zhuǎn)換,當(dāng)格式化日期時(shí),使用 utc 或 localtime 修飾符,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 常用函數(shù) # ==================================================================================== print('='*30) print('SQLite 常用函數(shù)') print('='*30) con = sqlite3.connect(":memory:") c = con.cursor() # Create table c.execute('''CREATE TABLE COMPANY (ID integer, NAME text, AGE integer, ADDRESS text, SALARY real)''') # Larger example that inserts many records at a time purchases = [(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 changes con.commit() # 返回?cái)?shù)據(jù)庫表最后 n 行記錄 # 先計(jì)算一個(gè)數(shù)據(jù)庫表中的行數(shù) c.execute("SELECT count(*) FROM COMPANY;") last = c.fetchone()[0] n = 5 c.execute("SELECT * FROM COMPANY LIMIT ? OFFSET ?;", (n, last-n)) for row in c: print(row) # 計(jì)算一個(gè)數(shù)據(jù)庫表中的行數(shù) c.execute("SELECT count(*) FROM COMPANY;") print(c.fetchone()) # 選擇某列的最大值 c.execute("SELECT max(salary) FROM COMPANY;") print(c.fetchone()) # 選擇某列的最小值 c.execute("SELECT min(salary) FROM COMPANY;") print(c.fetchone()) # 計(jì)算某列的平均值 c.execute("SELECT avg(salary) FROM COMPANY;") print(c.fetchone()) # 為一個(gè)數(shù)值列計(jì)算總和 c.execute("SELECT sum(salary) FROM COMPANY;") print(c.fetchone()) # 返回一個(gè)介于 -9223372036854775808 和 +9223372036854775807 之間的偽隨機(jī)整數(shù) c.execute("SELECT random() AS Random;") print(c.fetchone()) # 返回?cái)?shù)值參數(shù)的絕對值 c.execute("SELECT abs(5), abs(-15), abs(NULL), abs(0), abs('ABC');") print(c.fetchone()) # 把字符串轉(zhuǎn)換為大寫字母 c.execute("SELECT upper(name) FROM COMPANY;") print(c.fetchone()) # 把字符串轉(zhuǎn)換為小寫字母 c.execute("SELECT lower(name) FROM COMPANY;") print(c.fetchone()) # 返回字符串的長度 c.execute("SELECT name, length(name) FROM COMPANY;") print(c.fetchone()) # 返回 SQLite 庫的版本 c.execute("SELECT sqlite_version() AS 'SQLite Version';") print(c.fetchone()) # c.execute("SELECT CURRENT_TIMESTAMP;") print(c.fetchone())
PS:這里再為大家推薦2款SQL工具,附帶常用語句,供大家參考:
SQL在線壓縮/格式化工具:
http://tools.jb51.net/code/sql_format_compress
在線SQL格式化/壓縮工具:
http://tools.jb51.net/code/sql_fmt_yasuo
另:關(guān)于時(shí)間戳轉(zhuǎn)換還可參考本站時(shí)間戳轉(zhuǎn)換工具(附帶各種常用編程語言時(shí)間戳操作):
Unix時(shí)間戳(timestamp)轉(zhuǎn)換工具:
http://tools.jb51.net/code/unixtime
更多關(guān)于Python相關(guān)內(nèi)容感興趣的讀者可查看本站專題:《Python操作SQLite數(shù)據(jù)庫技巧總結(jié)》、《Python日期與時(shí)間操作技巧總結(jié)》、《Python常見數(shù)據(jù)庫操作技巧匯總》、《Python數(shù)據(jù)結(jié)構(gòu)與算法教程》、《Python函數(shù)使用技巧總結(jié)》、《Python字符串操作技巧匯總》、《Python入門與進(jìn)階經(jīng)典教程》及《Python文件與目錄操作技巧匯總》
希望本文所述對大家Python程序設(shè)計(jì)有所幫助。
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