python - 如何检查表是否存在？

I'm using this function :

我正在使用这个功能：

def checker(name,s)
        MY_T = "SELECT count(*) FROM `"+session.SessionInfo.Name where EventName='"+name+"'"

I want to check if the table exists, how can I do it ? I saw some examples using : XXXX.execute() what does it mean?

我想检查表是否存在，我该怎么办？我看到一些使用的例子：XXXX.execute（）是什么意思？

Here is what I saw :

这是我看到的：

query = cursor.execute("""SELECT count(*) FROM scan WHERE prefix = %s and code_id = %s and answer = %s and station_id = %s""",
                          (prefix, code_id, answer, station,))
        if query != 1:

I tried printing MY_T to see if it returns -1 for example but it just prints "select count (*)...... "

我尝试打印MY_T以查看它是否返回-1，但它只是打印“select count（*）......”

How can I check it? Any help would be very appreciated.

我怎么检查呢？任何帮助将非常感激。

3 个解决方案

#1

Use the "TABLES" information schema view. http://dev.mysql.com/doc/refman/5.0/en/information-schema.html

使用“TABLES”信息架构视图。 http://dev.mysql.com/doc/refman/5.0/en/information-schema.html

SELECT * FROM information_schema.tables
WHERE table_name = 'YOUR TABLE'

You can apply this view to your code by doing something like the following:

您可以通过执行以下操作将此视图应用于您的代码：

def checkTableExists(dbcon, tablename):
    dbcur = dbcon.cursor()
    dbcur.execute("""
        SELECT COUNT(*)
        FROM information_schema.tables
        WHERE table_name = '{0}'
        """.format(tablename.replace('\'', '\'\'')))
    if dbcur.fetchone()[0] == 1:
        dbcur.close()
        return True

    dbcur.close()
    return False

#2

If you are using Python-MySQL (MySQLdb) -> http://mysql-python.sourceforge.net/MySQLdb.html

如果您使用的是Python-MySQL（MySQLdb） - > http://mysql-python.sourceforge.net/MySQLdb.html

cursor.execute() is the method to run queries with MySQLdb, Python MySQL driver. You can pass two arguments, like:

cursor.execute（）是使用MySQLdb，Python MySQL驱动程序运行查询的方法。您可以传递两个参数，例如：

cursor.execute(statement, parameters)

And will execute "statement" parsing "parameters" to the statement. You need to have opened a database connection and also open a cursor

并将执行“语句”解析“参数”到语句。您需要打开数据库连接并打开游标

I think you can use MySQL's statement: SHOW TABLES LIKE 'tablename';

我想你可以使用MySQL的声明：SHOW TABLES LIKE'tablename';

stmt = "SHOW TABLES LIKE 'tableName'"
cursor.execute(stmt)
result = cursor.fetchone()
if result:
    # there is a table named "tableName"
else:
    # there are no tables named "tableName"

EDIT: there will other Python drivers with similar behaviour. Look for yours :)

编辑：将有其他类似行为的Python驱动程序。找你的:)

#3

I found that this works well with Python 3.6 and MySql 5.7:

我发现这适用于Python 3.6和MySql 5.7：

table = 'myTable'
_SQL = """SHOW TABLES"""
cursor.execute(_SQL)
results = cursor.fetchall()

print('All existing tables:', results) # Returned as a list of tuples

results_list = [item[0] for item in results] # Conversion to list of str

if table in results_list:
    print(table, 'was found!')
else:
    print(table, 'was NOT found!')

#1