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How can you test if some record exists or not in a MySQL table using Python?
We may at times need to check if a particular record exists in a table or not.
This can de done using the EXISTS statement. The EXISTS statement returns true if the following subquery returns one or more records.
Syntax
SELECT * FROM table_name WHERE EXISTS(sub_query)
The subquery if returns one or more rows, the EXISTS will return true.
Steps to check if a record exists in a table using MySQL in python
import MySQL connector
establish connection with the connector using connect()
create the cursor object using cursor() method
create a query using the appropriate mysql statements
execute the SQL query using execute() method
close the connection
Suppose we have the following table named “Sales”
+------------+---------+ | sale_price | tax | +------------+---------+ | 1000 | 200 | | 500 | 100 | | 50 | 50 | | 180 | 180 | +------------+---------+
Example
import mysql.connector db=mysql.connector.connect(host="your host", user="your username", password="your password",database="database_name") cursor=db.cursor() query="SELECT sale_price FROM Sales WHERE EXISTS(SELECT * FROM Sales WHERE tax>150)" cursor.execute(query) rows=cursor.fetchall() for row in rows: print(row) db.close()
The subquery in the above code returns TRUE since there are records where the tax is greater than 150. Thus the EXISTS statement returns true. If there were no records with tax greater than 150, then the EXISTS would have returned false.
Output
1000 500 700
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