是否可以使用OFFSET和乘法来分页查询？

Question

是否可以在查询中将两个数字相乘以进行分页MYSQL查询？

for z in zipcodes:

    # gets the website to find the closest big city
    res = requests.get('https://www.travelmath.com/cities-near/' + z)
    soup = bs4.BeautifulSoup(res.text, 'html.parser')
    elems = soup.select('#EchoTopic > div:nth-child(1) > ul:nth-child(8) > li:nth-child(1) > a:nth-child(2)')
    place = elems[0].text.strip()
    city, state = place.split(',')

    # uses the city found above to find the text in the webpage and the region it corresponds to
    newres = requests.get('https://www.almanac.com/weather/longrange')
    newsoup = bs4.BeautifulSoup(newres.text, 'html.parser')
    newelems = newsoup.find('td', text=city).parent.parent
    alltext = newelems.text
    region = find_region(alltext) # helper regex function I wrote

    # appends the zip code, city, and region to the DataFrame
    regions.append([z, city, region])

当我尝试在SQL中动态地对这两个数字进行乘法运算时，在乘法部分遇到了关于我的语法的错误。在查询中不能乘以数字吗？

我的完整查询

SELECT * FROM Posts
LIMIT $itemsPerPage
OFFSET ($pageNumber * $itemsPerPage)

例如，上面的SELECT com_id, time_stamp, comBy, post_id, comContent, IFNULL(likes, 0) - IFNULL(dislikes, 0) AS likeResult, profile_pic FROM Comments C # Adding Likes LEFT JOIN (SELECT likedCom_id, COUNT(*) AS likes FROM Comment_Likes GROUP BY likedCom_id) Cl ON C.com_id=Cl.likedCom_id LEFT JOIN (SELECT dislikedCom_id, IFNULL(COUNT(*),0) AS dislikes FROM Comment_Dislikes GROUP BY dislikedCom_id) Cd ON C.com_id=Cd.dislikedCom_id LEFT JOIN (SELECT user_id, profile_pic FROM Users) U ON U.user_id = C.comBy WHERE post_id = '10' ORDER BY time_stamp DESC LIMIT 5 OFFSET (0 * 5) 代码分别表示pageNumber和itemsPerPage变量。

我在HeidiSQL上遇到有关我的查询的错误：

Answer 1

OFFSET参数是标量值，提供数字文字或单个绑定值。

如果需要进行乘法运算，则可以在客户端中进行乘法运算，并将结果作为单个参数提供给OFFSET。

似乎代码正在动态生成SQL语句。我们可以做这样的事情：

$sql =  "SELECT ... OFFSET " . (int)($pageNumber * $itemsPerPage) ;

或

$offset = $pageNumber * $itemsPerPage ;
$sql =  "SELECT ... OFFSET " . (int)$offset ;

Answer 2

您需要限制，并且不能使用计算来通过限制或偏移量。.
（您可以使用dinamic sql）

在select sintax中，OFFSET是LIMIT子句中的一个子句
https://dev.mysql.com/doc/refman/8.0/en/select.html#id4651990

[LIMIT {[offset,] row_count | row_count OFFSET offset}]

my_valuse  = pageNumber * itemsPerPage; 

'SELECT * FROM Posts
LIMIT 100 OFFSET ' + my_value 

，您应该使用

'SELECT * 
FROM Posts
ORDER BY your_col
LIMIT 100 OFFSET ' + my_value