MySql SELECT * FROM table_name WHERE col_name IN（任何值）

Question

I am dynamically generating a python tuple

x = (1, 3)

So I can use MySql query in python like below,

f"SELECT * FROM table_name WHERE col_name IN {x}"

and it worked without problem.

But when I use empty tuple as x ( x = () ), I want the query to return all values of the table (just ignore the condition)

I know that I can use a if in python and pass the filter to sql only if x is not null. But I want to use this in sql so it will be easier because the actual query string is so long and has the same problem in many places.

So my question is,

IS THERE A WAY IN MYSQL LIKE BELOW,

SELECT * FROM table_name WHERE col_name IN (%)

just like we use

SELECT * FROM table_name WHERE col_name LIKE "%"

Answer 1

Came up with this python way. define a function like so:

def queryfriendly(value):
    if isinstance(value, str):
        return f'"{value}"'
    return str(value)

def tuple_to_condition(col_name, tup):
    if len(tup):
        return f'{col_name} IN (' + ', '.join(list(map(queryfriendly, tup))) + ')'
    return 'TRUE'

Now in your query strings do this:

f"SELECT * FROM table_name WHERE {tuple_to_condition('col_name', x)}"

The function just returns 'TRUE' so that the WHERE won't throw an error.

Answer 2

def sql_escape(s, replace_all=False):
if replace_all:
    s = s.replace("_", "\\_").replace("%", "\\%")
return s.replace("\\", "\\\\") \
    .replace("\'", "\\\'") \
    .replace("\"", "\\\"")
def sql_in(col, values, default="TRUE"):
    if values is None:
        return default
    values = set(values) - {""}
    if len(values):
        values = ",".join("\'" + sql_escape(str(v).strip()).replace("%", "\\%").replace("_", "\\_") + "\'"
                          for v in values)
        return f"{col} IN ({values})"
    else:
        return default

Answer 3

After trying out some codes, I found this as the answer.

x = [value1, value 2] # a list,, not a tuple
x.append("some value that does not in table")
x = tuple(x)

So the tuple won't be null. Now we can get a help from eshirvana's answer

SELECT * FROM table_name WHERE col_name IN {x} OR {len(x) > 1}