Query to execute expressions in SQLAlchemy Core
In this article, we can discuss how to use execute function to executeSQLAlchemy core expressions and conventional SQL queries.
Example 1:
SQLAlchemy provides a function called text(). We can write any conventional SQL query inside the text function enclosed by “”. Now, passing this SQL query to execute function will convert this query to SQLAlchemy compatible format and returns the result.
from sqlalchemy import text text("YOUR SQL QUERY")
Pass the SQL query to the execute() function and get all the results using fetchall() function. Use a for loop to iterate through the results. The SQLAlchemy query shown in the below code selects all rows where the book price is greater than Rs. 100.
Python3
# write the SQL query inside the text() block sql = text( 'SELECT * from BOOKS WHERE BOOKS.book_price > 100' ) results = engine.execute(sql) # Fetch all the records result = engine.execute(sql).fetchall() # View the records for record in result: print ( "\n" , record) |
Output:
Example 2:
The below query returns the book_price which is exactly equal divisible by 10
Python3
# write the SQL query inside the text() block sql = text( "SELECT * from BOOKS WHERE BOOKS.book_price/10 =10" ) # Fetch all the records result = engine.execute(sql).fetchall() # View the records for record in result: print ( "\n" , record) |
Output:
Example 3:
The below SQL expression will insert additional records in the created table using SQLAlchemy core.
from sqlalchemy import insert insert(table_name).values(column_name="value")
Get the books table from the Metadata object initialized while connecting to the database. Pass the insert query to the execute() function and get all the results using fetchall() function. Use a for loop to iterate through the results.
The SQLAlchemy query shown in the below code inserts additional records in the created table using SQLAlchemy core. Then, we can write a conventional SQL query and use fetchall() to print the results to check whether the table is updated properly.
Python3
# Get the `books` table from the Metadata object BOOKS = meta.tables[ 'books' ] from sqlalchemy import insert # write the insert statement stmt1 = insert(BOOKS).values(book_id = 6 , book_price = 400 , genre = "fiction" , book_name = "yoga is science" ) stmt2 = insert(BOOKS).values(book_id = 7 , book_price = 800 , genre = "non-fiction" , book_name = "alchemy tutorials" ) # execute engine.execute(stmt1) engine.execute(stmt2) # write the SQL query to check # whether the records are inserted sql = text( "SELECT * FROM BOOKS " ) results = engine.execute(sql) # View the records for record in results: print ( "\n" , record) |
Output:
Example 4:
Let us see another example related to updating query.
Tablename.update().where(Tablename.c.column_name == ‘value’).values(column_name = ‘value’)
Get the books table from the Metadata object initialized while connecting to the database. Pass the delete query to the execute() function and get all the results using fetchall() function. Use a for loop to iterate through the results.
The SQLAlchemy query shown in the below code updates the genre “non-fiction” as “sci-fi” this will effectively update multiple rows at one go. Then, we can write a conventional SQL query and use fetchall() to print the results to check whether the table is updated properly.
Python3
# Get the `books` table from the Metadata object BOOKS = meta.tables[ 'books' ] # update stmt = BOOKS.update().where(BOOKS.c.genre = = 'non-fiction' ).values(genre = 'sci-fi' ) engine.execute(stmt) # write the SQL query inside the # text() block to fetch all records sql = text( "SELECT * from BOOKS" ) # Fetch all the records result = engine.execute(sql).fetchall() # View the records for record in result: print ( "\n" , record) |
Output:
SQLAlchemy Core – Executing Expression
In this article, we are going to see how to execute SQLAlchemy core expression using Python.