Connecting a Db2 database
You can use a Db2 database as a data source for your GraphQL API by extending your
GraphQL API with the @dbquery
directive.
Any Query
or Mutation
field in your GraphQL schema can be
annotated with the @dbquery
directive to connect to a database backend.
@dbquery (type: String!, query: String, dml: enum, table: String, configuration: String!)
For more information on the @dbquery
directive, see Directives.
Use the arguments in the following sections when you want to connect to a Db2 database as a data source for your GraphQL API.
type
Required. This argument specifies the type of database to query. Supported values are
mysql
, postgresql
, mssql
, trino
,
presto
, singlestore
, db2
, and
snowflake
.
table
Optional. The value of this argument is the name of the database table to be queried. While this
value is optional, one of either table
or query
must be
specified.
Using the table
argument is the equivalent of writing select * from
[table]
. The field names of the GraphQL type of the annotated field must match the column
names of the underlying database table. Thus, if the table has a NAME
column, it
will populate the NAME
field of the GraphQL type.
If the annotated field has arguments, they are used to construct the WHERE
clause of the SQL query. For example, let's look at the following annotated field:
customerById (id: ID!): Customer
@dbquery (
type: "db2"
table: "customers"
configuration: "db2_config"
)
This example passes the following database query to the database specified by the
db2_config
configuration (See Managing backend connections for more
information about configurations).
SELECT "id", "name", "email", "creditCard" FROM "customers" WHERE "id" = ?
where id
, name
, email
and
creditCard
are the columns of the Db2 customers
table that match
the fields of the Customer
type.
If the annotated field has multiple arguments, they are combined in the SQL
WHERE
clause with an AND
.
query
Optional. The value of this argument is the SQL query whose results are used to populate the
sub-fields of the annotated field. While this value is optional, one of either
table
or query
must be specified.
The query
argument is useful when you need to perform a complex query, or when
the table column names and GraphQL type fields do not match. For example:
customerById (id: ID!): Customer
@dbquery (
type: "db2",
query: 'SELECT "id", "full_name" AS "name", "email" FROM "customer" WHERE "id" = ? AND "creditCard" is not NULL',
configuration: "db2_config"
)
The directive executes the specified SQL query
on the database specified by the
db2_config
. The SQL query both renames full_name
to
name
so it matches the field name in the GraphQL type Customer
,
and retrieves only those customers who have a credit card.
configuration
Required. This argument identifies which configuration in the config.yaml
file
should be used to connect to the database.
A Db2 database configuration contains the url
for connecting to your database,
and will look similar to this:
configurationset:
- configuration:
name: db2_config
url: jdbc:db2://<host>:<port>/<database>:user=<user>;password=<password>;sslConnection=<true/false>;
currentSchema=<schema>
In this example, db2_config
is the named configuration that will be referenced
by the configuration
property of @dbquery
as
configuration: db2_config
.
To learn more about the configuration settings for connecting to your Db2 database, see Db2 configuration.
dml
Optional. Use this argument when the annotated field is a mutation. Its value is an enum that
specifies the type of mutation being performed. Valid values are INSERT
and
DELETE
(do not enclose the value in quotation marks because it is an enum).
The following is an example of a mutation with a annotated field whose dml
argument value is INSERT
:
type Mutation {
addCustomerById(id: ID!, name: String!, email: String!): Customer
@dbquery(
type: "db2"
table: "customer"
dml: INSERT
configuration: "db2_config"
)
}
The selection of the addCustomer
field of this mutation results in the execution
of an insert statement followed by a select statement in the database Backend, adding the customer
and using the inserted values to populate the returned GraphQL Customer
type:
SELECT "id", "name", "email" FROM FINAL TABLE (INSERT INTO "customer"("id", "name", "email") VALUES (?, ?, ?))
Next, let's look at an example of using DELETE
:
type Mutation {
removeCustomerById(id: ID!): Customer
@dbquery(
type: "db2"
table: "customer"
dml: DELETE
configuration: "db2_config"
)
}
The selection of the removeCustomerById
field of this mutation results in the
execution of a select statement followed by a delete statement in the Db2 backend, resulting in the
removal of the customer with the specified id
and using the deleted values to
populate the returned GraphQL Customer
type:
SELECT "id", "name", "email" FROM OLD TABLE (DELETE FROM "customer" WHERE "id" = ?)