How to better prompt when doing SQL question-answering
In this guide we'll go over prompting strategies to improve SQL query generation usingcreate_sql_query_chain. We'll largely focus on methods for getting relevant database-specific information in your prompt.
We will cover:
- How the dialect of the LangChainSQLDatabase impacts the prompt of the chain;
- How to format schema information into the prompt using
SQLDatabase.get_context; - How to build and selectfew-shot examples to assist the model.
Setup
First, get required packages and set environment variables:
%pip install--upgrade--quiet langchain langchain-community langchain-experimental langchain-openai
# Uncomment the below to use LangSmith. Not required.
# import os
# os.environ["LANGSMITH_API_KEY"] = getpass.getpass()
# os.environ["LANGSMITH_TRACING"] = "true"
The below example will use a SQLite connection with Chinook database. Followthese installation steps to createChinook.db in the same directory as this notebook:
- Savethis file as
Chinook_Sqlite.sql - Run
sqlite3 Chinook.db - Run
.read Chinook_Sqlite.sql - Test
SELECT * FROM Artist LIMIT 10;
Now,Chinook.db is in our directory and we can interface with it using the SQLAlchemy-drivenSQLDatabase class:
from langchain_community.utilitiesimport SQLDatabase
db= SQLDatabase.from_uri("sqlite:///Chinook.db", sample_rows_in_table_info=3)
print(db.dialect)
print(db.get_usable_table_names())
print(db.run("SELECT * FROM Artist LIMIT 10;"))
API Reference:SQLDatabase
sqlite
['Album', 'Artist', 'Customer', 'Employee', 'Genre', 'Invoice', 'InvoiceLine', 'MediaType', 'Playlist', 'PlaylistTrack', 'Track']
[(1, 'AC/DC'), (2, 'Accept'), (3, 'Aerosmith'), (4, 'Alanis Morissette'), (5, 'Alice In Chains'), (6, 'Antônio Carlos Jobim'), (7, 'Apocalyptica'), (8, 'Audioslave'), (9, 'BackBeat'), (10, 'Billy Cobham')]
Dialect-specific prompting
One of the simplest things we can do is make our prompt specific to the SQL dialect we're using. When using the built-increate_sql_query_chain andSQLDatabase, this is handled for you for any of the following dialects:
from langchain.chains.sql_database.promptimport SQL_PROMPTS
list(SQL_PROMPTS)
['crate',
'duckdb',
'googlesql',
'mssql',
'mysql',
'mariadb',
'oracle',
'postgresql',
'sqlite',
'clickhouse',
'prestodb']
For example, using our current DB we can see that we'll get a SQLite-specific prompt.
Selectchat model:
pip install -qU "langchain[google-genai]"
import getpass
import os
ifnot os.environ.get("GOOGLE_API_KEY"):
os.environ["GOOGLE_API_KEY"]= getpass.getpass("Enter API key for Google Gemini: ")
from langchain.chat_modelsimport init_chat_model
llm= init_chat_model("gemini-2.0-flash", model_provider="google_genai")
from langchain.chainsimport create_sql_query_chain
chain= create_sql_query_chain(llm, db)
chain.get_prompts()[0].pretty_print()
API Reference:create_sql_query_chain
You are a SQLite expert. Given an input question, first create a syntactically correct SQLite query to run, then look at the results of the query and return the answer to the input question.
Unless the user specifies in the question a specific number of examples to obtain, query for at most 5 results using the LIMIT clause as per SQLite. You can order the results to return the most informative data in the database.
Never query for all columns from a table. You must query only the columns that are needed to answer the question. Wrap each column name in double quotes (") to denote them as delimited identifiers.
Pay attention to use only the column names you can see in the tables below. Be careful to not query for columns that do not exist. Also, pay attention to which column is in which table.
Pay attention to use date('now') function to get the current date, if the question involves "today".
Use the following format:
Question: Question here
SQLQuery: SQL Query to run
SQLResult: Result of the SQLQuery
Answer: Final answer here
Only use the following tables:
[33;1m[1;3m{table_info}[0m
Question: [33;1m[1;3m{input}[0m
Table definitions and example rows
In most SQL chains, we'll need to feed the model at least part of the database schema. Without this it won't be able to write valid queries. Our database comes with some convenience methods to give us the relevant context. Specifically, we can get the table names, their schemas, and a sample of rows from each table.
Here we will useSQLDatabase.get_context, which provides available tables and their schemas:
context= db.get_context()
print(list(context))
print(context["table_info"])
['table_info', 'table_names']
CREATE TABLE "Album" (
"AlbumId" INTEGER NOT NULL,
"Title" NVARCHAR(160) NOT NULL,
"ArtistId" INTEGER NOT NULL,
PRIMARY KEY ("AlbumId"),
FOREIGN KEY("ArtistId") REFERENCES "Artist" ("ArtistId")
)
/*
3 rows from Album table:
AlbumIdTitleArtistId
1For Those About To Rock We Salute You1
2Balls to the Wall2
3Restless and Wild2
*/
CREATE TABLE "Artist" (
"ArtistId" INTEGER NOT NULL,
"Name" NVARCHAR(120),
PRIMARY KEY ("ArtistId")
)
/*
3 rows from Artist table:
ArtistIdName
1AC/DC
2Accept
3Aerosmith
*/
CREATE TABLE "Customer" (
"CustomerId" INTEGER NOT NULL,
"FirstName" NVARCHAR(40) NOT NULL,
"LastName" NVARCHAR(20) NOT NULL,
"Company" NVARCHAR(80),
"Address" NVARCHAR(70),
"City" NVARCHAR(40),
"State" NVARCHAR(40),
"Country" NVARCHAR(40),
"PostalCode" NVARCHAR(10),
"Phone" NVARCHAR(24),
"Fax" NVARCHAR(24),
"Email" NVARCHAR(60) NOT NULL,
"SupportRepId" INTEGER,
PRIMARY KEY ("CustomerId"),
FOREIGN KEY("SupportRepId") REFERENCES "Employee" ("EmployeeId")
)
/*
3 rows from Customer table:
CustomerIdFirstNameLastNameCompanyAddressCityStateCountryPostalCodePhoneFaxEmailSupportRepId
1LuísGonçalvesEmbraer - Empresa Brasileira de Aeronáutica S.A.Av. Brigadeiro Faria Lima, 2170São José dos CamposSPBrazil12227-000+55 (12) 3923-5555+55 (12) 3923-5566luisg@embraer.com.br3
2LeonieKöhlerNoneTheodor-Heuss-Straße 34StuttgartNoneGermany70174+49 0711 2842222Noneleonekohler@surfeu.de5
3FrançoisTremblayNone1498 rue BélangerMontréalQCCanadaH2G 1A7+1 (514) 721-4711Noneftremblay@gmail.com3
*/
CREATE TABLE "Employee" (
"EmployeeId" INTEGER NOT NULL,
"LastName" NVARCHAR(20) NOT NULL,
"FirstName" NVARCHAR(20) NOT NULL,
"Title" NVARCHAR(30),
"ReportsTo" INTEGER,
"BirthDate" DATETIME,
"HireDate" DATETIME,
"Address" NVARCHAR(70),
"City" NVARCHAR(40),
"State" NVARCHAR(40),
"Country" NVARCHAR(40),
"PostalCode" NVARCHAR(10),
"Phone" NVARCHAR(24),
"Fax" NVARCHAR(24),
"Email" NVARCHAR(60),
PRIMARY KEY ("EmployeeId"),
FOREIGN KEY("ReportsTo") REFERENCES "Employee" ("EmployeeId")
)
/*
3 rows from Employee table:
EmployeeIdLastNameFirstNameTitleReportsToBirthDateHireDateAddressCityStateCountryPostalCodePhoneFaxEmail
1AdamsAndrewGeneral ManagerNone1962-02-18 00:00:002002-08-14 00:00:0011120 Jasper Ave NWEdmontonABCanadaT5K 2N1+1 (780) 428-9482+1 (780) 428-3457andrew@chinookcorp.com
2EdwardsNancySales Manager11958-12-08 00:00:002002-05-01 00:00:00825 8 Ave SWCalgaryABCanadaT2P 2T3+1 (403) 262-3443+1 (403) 262-3322nancy@chinookcorp.com
3PeacockJaneSales Support Agent21973-08-29 00:00:002002-04-01 00:00:001111 6 Ave SWCalgaryABCanadaT2P 5M5+1 (403) 262-3443+1 (403) 262-6712jane@chinookcorp.com
*/
CREATE TABLE "Genre" (
"GenreId" INTEGER NOT NULL,
"Name" NVARCHAR(120),
PRIMARY KEY ("GenreId")
)
/*
3 rows from Genre table:
GenreIdName
1Rock
2Jazz
3Metal
*/
CREATE TABLE "Invoice" (
"InvoiceId" INTEGER NOT NULL,
"CustomerId" INTEGER NOT NULL,
"InvoiceDate" DATETIME NOT NULL,
"BillingAddress" NVARCHAR(70),
"BillingCity" NVARCHAR(40),
"BillingState" NVARCHAR(40),
"BillingCountry" NVARCHAR(40),
"BillingPostalCode" NVARCHAR(10),
"Total" NUMERIC(10, 2) NOT NULL,
PRIMARY KEY ("InvoiceId"),
FOREIGN KEY("CustomerId") REFERENCES "Customer" ("CustomerId")
)
/*
3 rows from Invoice table:
InvoiceIdCustomerIdInvoiceDateBillingAddressBillingCityBillingStateBillingCountryBillingPostalCodeTotal
122021-01-01 00:00:00Theodor-Heuss-Straße 34StuttgartNoneGermany701741.98
242021-01-02 00:00:00Ullevålsveien 14OsloNoneNorway01713.96
382021-01-03 00:00:00Grétrystraat 63BrusselsNoneBelgium10005.94
*/
CREATE TABLE "InvoiceLine" (
"InvoiceLineId" INTEGER NOT NULL,
"InvoiceId" INTEGER NOT NULL,
"TrackId" INTEGER NOT NULL,
"UnitPrice" NUMERIC(10, 2) NOT NULL,
"Quantity" INTEGER NOT NULL,
PRIMARY KEY ("InvoiceLineId"),
FOREIGN KEY("TrackId") REFERENCES "Track" ("TrackId"),
FOREIGN KEY("InvoiceId") REFERENCES "Invoice" ("InvoiceId")
)
/*
3 rows from InvoiceLine table:
InvoiceLineIdInvoiceIdTrackIdUnitPriceQuantity
1120.991
2140.991
3260.991
*/
CREATE TABLE "MediaType" (
"MediaTypeId" INTEGER NOT NULL,
"Name" NVARCHAR(120),
PRIMARY KEY ("MediaTypeId")
)
/*
3 rows from MediaType table:
MediaTypeIdName
1MPEG audio file
2Protected AAC audio file
3Protected MPEG-4 video file
*/
CREATE TABLE "Playlist" (
"PlaylistId" INTEGER NOT NULL,
"Name" NVARCHAR(120),
PRIMARY KEY ("PlaylistId")
)
/*
3 rows from Playlist table:
PlaylistIdName
1Music
2Movies
3TV Shows
*/
CREATE TABLE "PlaylistTrack" (
"PlaylistId" INTEGER NOT NULL,
"TrackId" INTEGER NOT NULL,
PRIMARY KEY ("PlaylistId", "TrackId"),
FOREIGN KEY("TrackId") REFERENCES "Track" ("TrackId"),
FOREIGN KEY("PlaylistId") REFERENCES "Playlist" ("PlaylistId")
)
/*
3 rows from PlaylistTrack table:
PlaylistIdTrackId
13402
13389
13390
*/
CREATE TABLE "Track" (
"TrackId" INTEGER NOT NULL,
"Name" NVARCHAR(200) NOT NULL,
"AlbumId" INTEGER,
"MediaTypeId" INTEGER NOT NULL,
"GenreId" INTEGER,
"Composer" NVARCHAR(220),
"Milliseconds" INTEGER NOT NULL,
"Bytes" INTEGER,
"UnitPrice" NUMERIC(10, 2) NOT NULL,
PRIMARY KEY ("TrackId"),
FOREIGN KEY("MediaTypeId") REFERENCES "MediaType" ("MediaTypeId"),
FOREIGN KEY("GenreId") REFERENCES "Genre" ("GenreId"),
FOREIGN KEY("AlbumId") REFERENCES "Album" ("AlbumId")
)
/*
3 rows from Track table:
TrackIdNameAlbumIdMediaTypeIdGenreIdComposerMillisecondsBytesUnitPrice
1For Those About To Rock (We Salute You)111Angus Young, Malcolm Young, Brian Johnson343719111703340.99
2Balls to the Wall221U. Dirkschneider, W. Hoffmann, H. Frank, P. Baltes, S. Kaufmann, G. Hoffmann34256255104240.99
3Fast As a Shark321F. Baltes, S. Kaufman, U. Dirkscneider & W. Hoffman23061939909940.99
*/
When we don't have too many, or too wide of, tables, we can just insert the entirety of this information in our prompt:
prompt_with_context= chain.get_prompts()[0].partial(table_info=context["table_info"])
print(prompt_with_context.pretty_repr()[:1500])
You are a SQLite expert. Given an input question, first create a syntactically correct SQLite query to run, then look at the results of the query and return the answer to the input question.
Unless the user specifies in the question a specific number of examples to obtain, query for at most 5 results using the LIMIT clause as per SQLite. You can order the results to return the most informative data in the database.
Never query for all columns from a table. You must query only the columns that are needed to answer the question. Wrap each column name in double quotes (") to denote them as delimited identifiers.
Pay attention to use only the column names you can see in the tables below. Be careful to not query for columns that do not exist. Also, pay attention to which column is in which table.
Pay attention to use date('now') function to get the current date, if the question involves "today".
Use the following format:
Question: Question here
SQLQuery: SQL Query to run
SQLResult: Result of the SQLQuery
Answer: Final answer here
Only use the following tables:
CREATE TABLE "Album" (
"AlbumId" INTEGER NOT NULL,
"Title" NVARCHAR(160) NOT NULL,
"ArtistId" INTEGER NOT NULL,
PRIMARY KEY ("AlbumId"),
FOREIGN KEY("ArtistId") REFERENCES "Artist" ("ArtistId")
)
/*
3 rows from Album table:
AlbumIdTitleArtistId
1For Those About To Rock We Salute You1
2Balls to the Wall2
3Restless and Wild2
*/
CREATE TABLE "Artist" (
"ArtistId" INTEGER NOT NULL,
"Name" NVARCHAR(120)
When we do have database schemas that are too large to fit into our model's context window, we'll need to come up with ways of inserting only the relevant table definitions into the prompt based on the user input. For more on this head to theMany tables, wide tables, high-cardinality feature guide.
Few-shot examples
Including examples of natural language questions being converted to valid SQL queries against our database in the prompt will often improve model performance, especially for complex queries.
Let's say we have the following examples:
examples=[
{"input":"List all artists.","query":"SELECT * FROM Artist;"},
{
"input":"Find all albums for the artist 'AC/DC'.",
"query":"SELECT * FROM Album WHERE ArtistId = (SELECT ArtistId FROM Artist WHERE Name = 'AC/DC');",
},
{
"input":"List all tracks in the 'Rock' genre.",
"query":"SELECT * FROM Track WHERE GenreId = (SELECT GenreId FROM Genre WHERE Name = 'Rock');",
},
{
"input":"Find the total duration of all tracks.",
"query":"SELECT SUM(Milliseconds) FROM Track;",
},
{
"input":"List all customers from Canada.",
"query":"SELECT * FROM Customer WHERE Country = 'Canada';",
},
{
"input":"How many tracks are there in the album with ID 5?",
"query":"SELECT COUNT(*) FROM Track WHERE AlbumId = 5;",
},
{
"input":"Find the total number of invoices.",
"query":"SELECT COUNT(*) FROM Invoice;",
},
{
"input":"List all tracks that are longer than 5 minutes.",
"query":"SELECT * FROM Track WHERE Milliseconds > 300000;",
},
{
"input":"Who are the top 5 customers by total purchase?",
"query":"SELECT CustomerId, SUM(Total) AS TotalPurchase FROM Invoice GROUP BY CustomerId ORDER BY TotalPurchase DESC LIMIT 5;",
},
{
"input":"Which albums are from the year 2000?",
"query":"SELECT * FROM Album WHERE strftime('%Y', ReleaseDate) = '2000';",
},
{
"input":"How many employees are there",
"query":'SELECT COUNT(*) FROM "Employee"',
},
]
We can create a few-shot prompt with them like so:
from langchain_core.promptsimport FewShotPromptTemplate, PromptTemplate
example_prompt= PromptTemplate.from_template("User input: {input}\nSQL query: {query}")
prompt= FewShotPromptTemplate(
examples=examples[:5],
example_prompt=example_prompt,
prefix="You are a SQLite expert. Given an input question, create a syntactically correct SQLite query to run. Unless otherwise specificed, do not return more than {top_k} rows.\n\nHere is the relevant table info: {table_info}\n\nBelow are a number of examples of questions and their corresponding SQL queries.",
suffix="User input: {input}\nSQL query: ",
input_variables=["input","top_k","table_info"],
)
API Reference:FewShotPromptTemplate |PromptTemplate
print(prompt.format(input="How many artists are there?", top_k=3, table_info="foo"))
You are a SQLite expert. Given an input question, create a syntactically correct SQLite query to run. Unless otherwise specificed, do not return more than 3 rows.
Here is the relevant table info: foo
Below are a number of examples of questions and their corresponding SQL queries.
User input: List all artists.
SQL query: SELECT * FROM Artist;
User input: Find all albums for the artist 'AC/DC'.
SQL query: SELECT * FROM Album WHERE ArtistId = (SELECT ArtistId FROM Artist WHERE Name = 'AC/DC');
User input: List all tracks in the 'Rock' genre.
SQL query: SELECT * FROM Track WHERE GenreId = (SELECT GenreId FROM Genre WHERE Name = 'Rock');
User input: Find the total duration of all tracks.
SQL query: SELECT SUM(Milliseconds) FROM Track;
User input: List all customers from Canada.
SQL query: SELECT * FROM Customer WHERE Country = 'Canada';
User input: How many artists are there?
SQL query:
Dynamic few-shot examples
If we have enough examples, we may want to only include the most relevant ones in the prompt, either because they don't fit in the model's context window or because the long tail of examples distracts the model. And specifically, given any input we want to include the examples most relevant to that input.
We can do just this using an ExampleSelector. In this case we'll use aSemanticSimilarityExampleSelector, which will store the examples in the vector database of our choosing. At runtime it will perform a similarity search between the input and our examples, and return the most semantically similar ones.
We default to OpenAI embeddings here, but you can swap them out for the model provider of your choice.
from langchain_community.vectorstoresimport FAISS
from langchain_core.example_selectorsimport SemanticSimilarityExampleSelector
from langchain_openaiimport OpenAIEmbeddings
example_selector= SemanticSimilarityExampleSelector.from_examples(
examples,
OpenAIEmbeddings(),
FAISS,
k=5,
input_keys=["input"],
)
example_selector.select_examples({"input":"how many artists are there?"})
[{'input': 'List all artists.', 'query': 'SELECT * FROM Artist;'},
{'input': 'How many employees are there',
'query': 'SELECT COUNT(*) FROM "Employee"'},
{'input': 'How many tracks are there in the album with ID 5?',
'query': 'SELECT COUNT(*) FROM Track WHERE AlbumId = 5;'},
{'input': 'Which albums are from the year 2000?',
'query': "SELECT * FROM Album WHERE strftime('%Y', ReleaseDate) = '2000';"},
{'input': "List all tracks in the 'Rock' genre.",
'query': "SELECT * FROM Track WHERE GenreId = (SELECT GenreId FROM Genre WHERE Name = 'Rock');"}]
To use it, we can pass the ExampleSelector directly in to our FewShotPromptTemplate:
prompt= FewShotPromptTemplate(
example_selector=example_selector,
example_prompt=example_prompt,
prefix="You are a SQLite expert. Given an input question, create a syntactically correct SQLite query to run. Unless otherwise specificed, do not return more than {top_k} rows.\n\nHere is the relevant table info: {table_info}\n\nBelow are a number of examples of questions and their corresponding SQL queries.",
suffix="User input: {input}\nSQL query: ",
input_variables=["input","top_k","table_info"],
)
print(prompt.format(input="how many artists are there?", top_k=3, table_info="foo"))
You are a SQLite expert. Given an input question, create a syntactically correct SQLite query to run. Unless otherwise specificed, do not return more than 3 rows.
Here is the relevant table info: foo
Below are a number of examples of questions and their corresponding SQL queries.
User input: List all artists.
SQL query: SELECT * FROM Artist;
User input: How many employees are there
SQL query: SELECT COUNT(*) FROM "Employee"
User input: How many tracks are there in the album with ID 5?
SQL query: SELECT COUNT(*) FROM Track WHERE AlbumId = 5;
User input: Which albums are from the year 2000?
SQL query: SELECT * FROM Album WHERE strftime('%Y', ReleaseDate) = '2000';
User input: List all tracks in the 'Rock' genre.
SQL query: SELECT * FROM Track WHERE GenreId = (SELECT GenreId FROM Genre WHERE Name = 'Rock');
User input: how many artists are there?
SQL query:
Trying it out, we see that the model identifies the relevant table:
chain= create_sql_query_chain(llm, db, prompt)
chain.invoke({"question":"how many artists are there?"})
'SELECT COUNT(*) FROM Artist;'