mysql error syntax in python

Question

sql = """
DROP PROCEDURE
IF EXISTS schema_change;

delimiter ';;'
CREATE PROCEDURE schema_change() BEGIN

    if exists (select * from information_schema.columns where table_schema = 
    schema() and table_name = 'selectedairport' and column_name = 'GDP') 
    then
        alter table selectedairport drop column GDP;

    alter table selectedairport add column GDP DOUBLE;

end;;

delimiter ';'


CALL schema_change () ; DROP PROCEDURE
IF EXISTS schema_change ;
"""
cursor6.execute(sql)

However, this produces the error:

pymysql.err.ProgrammingError: (1064, "You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'delimiter ';;'\nCREATE PROCEDURE schema_change() BEGIN\n\n if exists (select * f' at line 1")

What could be the problem?

Answer 1

The execute() method (usually) only executes a single command at a time, so the script cannot be parsed, and anyway there is no support for DELIMITER; see this comment on GitHub. Therefore, one solution is to have multiple calls:

cursor6.execute("""
DROP PROCEDURE
IF EXISTS schema_change
""")

cursor6.execute("""
CREATE PROCEDURE schema_change() BEGIN

    if exists (select * from information_schema.columns where table_schema = 
    schema() and table_name = 'selectedairport' and column_name = 'GDP') 
    then
        alter table selectedairport drop column GDP;

NOTE: There is a syntax error here, we need to further add:

    END IF;

Now continue as before:

    alter table selectedairport add column GDP DOUBLE;

end
""")

cursor6.execute("""
CALL schema_change () 
""")

# Or cursor6.callproc('schema_change')

cursor6.execute("""
DROP PROCEDURE
IF EXISTS schema_change
""")