Python为MySQL创建动态选择语句

Question

In my MySQL database I have 10 tables. Based on the user input, I want to select the rows from one of the table. The user input is an image. I am getting the number of columns and rows of pixels the image has and storing it in a variable.

rows,cols,channels = img.shape
w = int(cols)
h = int(rows)
l = w-10
m = w+10
p = h-10
q = h+10
area = w*h

the mysql tables are created basis the area of the image, and hence, depending on the area, I want to select the values from a specific table.

if (area < 110980):
        sql = "select * from adf1 where WIDTH between %s and %s and HEIGHT between %s and %s;",(l,m,p,q)
    elif (area < 182520):
        sql = "select * from adf2 where WIDTH between %s and %s and HEIGHT between %s and %s;",(l,m,p,q)
else:
        sql = "select * from adf10 where WIDTH between %s and %s and HEIGHT between %s and %s;",(l,m,p,q)
cur = mysql.connect().cursor()
cur.execute(sql)

I am getting the following error:

TypeError: cannot concatenate 'str' and 'tuple' objects

However, when I pass on a single query within cur.execute I am able to retrieve the results.

cur.execute("select * from adf10 where WIDTH between %s and %s and HEIGHT between %s and %s;",(l,m,p,q))

Answer 1

current your variable sql is tuple, so if you want to pass it as parameters to the execute you should use *

cur.execute(*sql)

you can read more in the doc unpacking-argument-lists

Answer 2

this should fix your problem. You need to use % not comma in the queries inside if else.

"select * from adf2 where WIDTH between %s and %s and HEIGHT between %s and %s;"%(l,m,p,q)