Develop Reference

Use of variable in SQL query

I want to use a variable in the Select Query but it give me a fail. Someone can guide me how to insert this variable in my SQL query ?
project = test
# Our SQL Query
Query_1 = """
SELECT * FROM project.dataplex_dq.dq-results`
"""
# labelling our query job
query_job_1 = client.query(Query_1)
# results as a dataframe
Table = query_job_1.result().to_dataframe()

Illegal Variable Name/Number when Passing in Python List

I'm trying to run SQL statements through Python on a list.
By passing in a list, in this case date. Since i want to run multiple SELECT SQL queries and return them.
I've tested this by passing in integers, however when trying to pass in a date I am getting ORA-01036 error. Illegal variable name/number. I'm using an Oracle DB.
cursor = connection.cursor()
date = ["'01-DEC-21'", "'02-DEC-21'"]
sql = "select * from table1 where datestamp = :date"
for item in date:
cursor.execute(sql,id=item)
res=cursor.fetchall()
print(res)
Any suggestions to make this run?

You can't name a bind variable date, it's an illegal name. Also your named variable in cursor.execute should match the bind variable name. Try something like:
sql = "select * from table1 where datestamp = :date_input"
for item in date:
cursor.execute(sql,date_input=item)
res=cursor.fetchall()
print(res)

Some recommendation and warnings to your approach:
you should not depend on your default NLS date setting, while binding a String (e.g. "'01-DEC-21'") to a DATE column. (You probably need also remone one of the quotes).
You should ommit to fetch data in a loop if you can fetch them in one query (using an IN list)
use prepared statement
Example
date = ['01-DEC-21', '02-DEC-21']
This generates the query that uses bind variables for your input list
in_list = ','.join([f" TO_DATE(:d{ind},'DD-MON-RR','NLS_DATE_LANGUAGE = American')" for ind, d in enumerate(date)])
sql_query = "select * from table1 where datestamp in ( " + in_list + " )"
The sql_query generate is
select * from table1 where datestamp in
( TO_DATE(:d0,'DD-MON-RR','NLS_DATE_LANGUAGE = American'), TO_DATE(:d1,'DD-MON-RR','NLS_DATE_LANGUAGE = American') )
Note that the INlist contains one bind variable for each member of your input list.
Note also the usage of to_date with explicite mask and fixing the language to avoid problems with interpretation of the month abbreviation. (e.g. ORA-01843: not a valid month)
Now you can use the query to fetch the data in one pass
cur.prepare(sql_query)
cur.execute(None, date)
res = cur.fetchall()

Python MySQL search entire database for value

I have a GUI interacting with my database, and MySQL database has around 50 tables. I need to search each table for a value and return the field and key of the item in each table if it is found. I would like to search for partial matches. ex.( Search Value = "test", "Protest", "Test123" would be matches. Here is my attempt.
def searchdatabase(self, event):
print('Searching...')
self.connect_mysql() #Function to connect to database
d_tables = []
results_list = [] # I will store results here
s_string = "test" #Value I am searching
self.cursor.execute("USE db") # select the database
self.cursor.execute("SHOW TABLES")
for (table_name,) in self.cursor:
d_tables.append(table_name)
#Loop through tables list, get column name, and check if value is in the column
for table in d_tables:
#Get the columns
self.cursor.execute(f"SELECT * FROM `{table}` WHERE 1=0")
field_names = [i[0] for i in self.cursor.description]
#Find Value
for f_name in field_names:
print("RESULTS:", self.cursor.execute(f"SELECT * FROM `{table}` WHERE {f_name} LIKE {s_string}"))
print(table)
I get an error on print("RESULTS:", self.cursor.execute(f"SELECT * FROM `{table}` WHERE {f_name} LIKE {s_string}"))
Exception: (1054, "Unknown column 'test' in 'where clause'")
I use a similar insert query that works fine so I am not understanding what the issue is.
ex. insert_query = (f"INSERT INTO `{source_tbl}` ({query_columns}) VALUES ({query_placeholders})")

May be because of single quote you have missed while checking for some columns.
TRY :
print("RESULTS:", self.cursor.execute(f"SELECT * FROM `{table}` WHERE '{f_name}' LIKE '{s_string}'"))
Have a look -> here

Don’t insert user-provided data into SQL queries like this. It is begging for SQL injection attacks. Your database library will have a way of sending parameters to queries. Use that.
The whole design is fishy. Normally, there should be no need to look for a string across several columns of 50 different tables. Admittedly, sometimes you end up in these situations because of reasons outside your control.

Alter query according to user selection in sqlite python

I have a sqlite database named StudentDB which has 3 columns Roll number, Name, Marks. Now I want to fetch only the columns that user selects in the IDE. User can select one column or two or all the three. How can I alter the query accordingly using Python?
I tried:
import sqlite3
sel={"Roll Number":12}
query = 'select * from StudentDB Where({seq})'.format(seq=','.join(['?']*len(sel))),[i for k,i in sel.items()]
con = sqlite3.connect(database)
cur = con.cursor()
cur.execute(query)
all_data = cur.fetchall()
all_data
I am getting:
operation parameter must be str

You should control the text of the query. The where clause shall allways be in the form WHERE colname=value [AND colname2=...] or (better) WHERE colname=? [AND ...] if you want to build a parameterized query.
So you want:
query = 'select * from StudentDB Where ' + ' AND '.join('"{}"=?'.format(col)
for col in sel.keys())
...
cur.execute(query, tuple(sel.values()))

In your code, the query is now a tuple instead of str and that is why the error.
I assume you want to execute a query like below -
select * from StudentDB Where "Roll number"=?
Then you can change the sql query like this (assuming you want and and not or) -
query = "select * from StudentDB Where {seq}".format(seq=" and ".join('"{}"=?'.format(k) for k in sel.keys()))
and execute the query like -
cur.execute(query, tuple(sel.values()))
Please make sure in your code the provided database is defined and contains the database name and studentDB is indeed the table name and not database name.

Update multiple postgresql records using unnest

I have a database table with nearly 1 million records.
I have added a new column, called concentration.
I then have a function which calculates 'concentration' for each record.
Now, I want to update the records in batch, so I have been looking at the following questions/answers: https://stackoverflow.com/a/33258295/596841, https://stackoverflow.com/a/23324727/596841 and https://stackoverflow.com/a/39626473/596841, but I am not sure how to do this using unnest...
This is my Python 3 function to do the updates:
def BatchUpdateWithConcentration(tablename, concentrations):
connection = psycopg2.connect(dbname=database_name, host=host, port=port, user=username, password=password);
cursor = connection.cursor();
sql = """
update #tablename# as t
set
t.concentration = s.con
FROM unnest(%s) s(con, id)
WHERE t.id = s.id;
"""
cursor.execute(sql.replace('#tablename#',tablename.lower()), (concentrations,))
connection.commit()
cursor.close()
connection.close()
concentrations is an array of tuples:
[(3.718244705238561e-16, 108264), (...)]
The first value is a double precision and the second is an integer, representing the concentration and rowid, respectively.
The error I'm getting is:
psycopg2.ProgrammingError: a column definition list is required for functions returning "record"
LINE 5: FROM unnest(ARRAY[(3.718244705238561e-16, 108264), (...
^

Since a Python tuple is adapted by Psycopg to a Postgresql anonymous record it is necessary to specify the data types:
from unnest(%s) s(con numeric, id integer)