Represents Varchar NVarchar  SQL field.



anydata|object {}|anydata[]|object {}[]?

value

TypedValue

Value of parameter passed into the SQL statement


string

init

NVarcharArrayValue

Represents Array Out Parameter used in procedure calls


Parses returned SQL value to ballerina value.



Type description of the data that need to be converted


typeDesc

ArrayOutParameter

Value of parameter passed into the SQL statement
# Deprecated
This `ArrayValue` class deprecated by introducing the a new `ArrayValueType` type.


ArrayValue

BigIntArrayValue

Represents BigInt Out Parameter used in procedure calls


BigIntOutParameter

BigIntValue

BinaryArrayValue

Represents Binary Out Parameter used in procedure calls


BinaryOutParameter

ReadableByteChannel

BinaryValue

BitArrayValue

Represents Bit Out Parameter used in procedure calls


BitOutParameter

boolean

BitValue

Represents Blob Out Parameter used in procedure calls


BlobOutParameter

BlobValue

BooleanArrayValue

Represents Boolean Out Parameter used in procedure calls


BooleanOutParameter

BooleanValue

CharArrayValue

Represents Char Out Parameter used in procedure calls


Parses returned Char SQL value to ballerina value.



CharOutParameter

CharValue

Represents Clob Out Parameter used in procedure calls


ClobOutParameter

ReadableCharacterChannel

ClobValue

DateArrayValue

Represents Date Out Parameter used in procedure calls


DateOutParameter

DateTimeArrayValue

Represents DateTime Out Parameter used in procedure calls


DateTimeOutParameter

Civil

DateTimeValue

Date

DateValue

DecimalArrayValue

Represents Decimal Out Parameter used in procedure calls


DecimalOutParameter

decimal

DecimalValue

DoubleArrayValue

Represents Double Out Parameter used in procedure calls


DoubleOutParameter

float

DoubleValue

FloatArrayValue

Represents Float Out Parameter used in procedure calls


FloatOutParameter

FloatValue

Represents SQL InOutParameter used in procedure calls.


Value

InOutParameter

IntegerArrayValue

Represents Integer Out Parameter used in procedure calls


IntegerOutParameter

IntegerValue

Represents NChar Out Parameter used in procedure calls


NCharOutParameter

NCharValue

Represents NClob Out Parameter used in procedure calls


NClobOutParameter

NClobValue

NumericArrayValue

Represents Numeric Out Parameter used in procedure calls


NumericOutParameter

NumericValue

Represents NVarchar Out Parameter used in procedure calls


NVarcharOutParameter

NVarcharValue

Object that is used to return stored procedure call results.



Summary of the execution of DML/DLL query


executionResult

ExecutionResult

queryResult

record {}

Error

stream

The instance of the custom Ballerina class that is structurally equivalent to
the `customResultIterator` object type. This instance includes a custom implementation
of the `getNextQueryResult` method


customResultIterator

CustomResultIterator

Updates `executionResult` or `queryResult` with the next result in the result. This will also close the current
results by default.



getNextQueryResult

True if the next result is `queryResult`


Closes the `sql:ProcedureCallResult` object and releases the associated resources.



close

An `sql:Error` if any error occurred while closing


ProcedureCallResult

RealArrayValue

Represents Real Out Parameter used in procedure calls


RealOutParameter

RealValue

Represents Ref Out Parameter used in procedure calls


RefOutParameter

RefValue

The result iterator object that is used to iterate through the results in the event stream.



The instance of the custom Ballerina class that is structurally equivalent to
the `customResultIterator` object type. This instance includes a custom implementation
of the `nextResult` method


ResultIterator

Represents Row Out Parameter used in procedure calls


RowOutParameter

byte

RowValue

SmallIntArrayValue

Represents SmallInt Out Parameter used in procedure calls


SmallIntOutParameter

SmallIntValue

Represents Struct Out Parameter used in procedure calls


StructOutParameter

StructValue

Represents Text Out Parameter used in procedure calls


TextOutParameter

TextValue

TimeArrayValue

Represents Time Out Parameter used in procedure calls


TimeOutParameter

TimestampArrayValue

Represents Timestamp Out Parameter used in procedure calls


TimestampOutParameter

TimestampValue

Represents Timestamp with Timezone Out Parameter used in procedure calls


TimestampWithTimezoneOutParameter

TimeOfDay

TimeValue

Represents Time With Timezone Out Parameter used in procedure calls


TimeWithTimezoneOutParameter

VarBinaryArrayValue

Represents VarBinary Out Parameter used in procedure calls


VarBinaryOutParameter

VarBinaryValue

VarcharArrayValue

Represents Varchar Out Parameter used in procedure calls


VarcharOutParameter

VarcharValue

Represents XML Out Parameter used in procedure calls


XMLOutParameter

Constant indicating that the specific batch statement failed.


EXECUTION_FAILED

Constant indicating that the specific batch statement executed successfully
but that no count of the number of rows it affected is available.


SUCCESS_NO_INFO

## Overview

This module provides the common interface and functionality to interact with a database. The corresponding database
clients can be created by using specific database modules such as `mysql` or using the Java Database Connectivity 
module `jdbc`.

### List of Database Modules
Ballerina now has the [`jdbc` module](https://docs.central.ballerina.io/ballerinax/java.jdbc/latest) as the generic DB connector module to connect to any relational database by simply providing the JDBC URL and the other related properties.
Ballerina also provides specially designed various database-specific DB connectors so that you can work with different databases and you can access their DB-specific functionalities.

### Client

The database client should be created using any of the above-listed database modules and once it is created, the operations and functionality explained below can be used. 

#### Connection Pool Handling

All database modules share the same connection pooling concept and there are three possible scenarios for 
connection pool handling.  For its properties and possible values, see the [`sql:ConnectionPool`](https://docs.central.ballerina.io/ballerina/sql/latest/records/ConnectionPool).  

1. Global, shareable, default connection pool

    If you do not provide the `poolOptions` field when creating the database client, a globally-shareable pool will be 
    created for your database unless a connection pool matching with the properties you provided already exists. 
    The JDBC module example below shows how the global connection pool is used. 

    ```ballerina
    jdbc:Client|sql:Error dbClient = 
                               new ("jdbc:mysql://localhost:3306/testdb", 
                                "root", "root");
    ```

2. Client-owned, unsharable connection pool

    If you define the `connectionPool` field inline when creating the database client with the `sql:ConnectionPool` type, 
    an unsharable connection pool will be created. The JDBC module example below shows how the global 
    connection pool is used.

    ```ballerina
    jdbc:Client|sql:Error dbClient = 
                               new (url = "jdbc:mysql://localhost:3306/testdb", 
                               connectionPool = { maxOpenConnections: 5 });
    ```

3. Local, shareable connection pool

    If you create a record of the `sql:ConnectionPool` type and reuse that in the configuration of multiple clients, 
    for each set of clients that connects to the same database instance with the same set of properties, a shared 
    connection pool will be created. The JDBC module example below shows how the global connection pool is used.

    ```ballerina
    sql:ConnectionPool connPool = {maxOpenConnections: 5};
    
    jdbc:Client|sql:Error dbClient1 =       
                               new (url = "jdbc:mysql://localhost:3306/testdb",
                               connectionPool = connPool);
    jdbc:Client|sql:Error dbClient2 = 
                               new (url = "jdbc:mysql://localhost:3306/testdb",
                               connectionPool = connPool);
    jdbc:Client|sql:Error dbClient3 = 
                               new (url = "jdbc:mysql://localhost:3306/testdb",
                               connectionPool = connPool);
    ```
    
#### Closing the Client

Once all the database operations are performed, you can close the database client you have created by invoking the `close()`
operation. This will close the corresponding connection pool if it is not shared by any other database clients. 

```ballerina
error? e = dbClient.close();
```
Or
```ballerina
check dbClient.close();
```

### Database Operations

Once the client is created, database operations can be executed through that client. This module defines the interface 
and common properties that are shared among multiple database clients.  It also supports querying, inserting, deleting, 
updating, and batch updating data.  

#### Creating Tables

This sample creates a table with two columns. One column is of type `int` and the other is of type `varchar`.
The `CREATE` statement is executed via the `execute` remote function of the client.

```ballerina
// Create the ‘Students’ table with the  ‘id’, 'name', and ‘age’ fields.
sql:ExecutionResult ret = check dbClient->execute("CREATE TABLE student(id INT AUTO_INCREMENT, " +
                         "age INT, name VARCHAR(255), PRIMARY KEY (id))");
//A value of the sql:ExecutionResult type is returned for 'ret'. 
```

#### Inserting Data

This sample shows three examples of data insertion by executing an `INSERT` statement using the `execute` remote function 
of the client.

In the first example, the query parameter values are passed directly into the query statement of the `execute` 
remote function.

```ballerina
sql:ExecutionResult ret = check dbClient->execute("INSERT INTO student(age, name) " +
                         "values (23, 'john')");
```

In the second example, the parameter values, which are in local variables are used to parameterize the SQL query in 
the `execute` remote function. This type of a parameterized SQL query can be used with any primitive Ballerina type 
like `string`, `int`, `float`, or `boolean` and in that case, the corresponding SQL type of the parameter is derived 
from the type of the Ballerina variable that is passed in. 

```ballerina
string name = "Anne";
int age = 8;

sql:ParameterizedQuery query = `INSERT INTO student(age, name)
                                values (${age}, ${name})`;
sql:ExecutionResult ret = check dbClient->execute(query);
```

In the third example, the parameter values are passed as a `sql:TypedValue` to the `execute` remote function. Use the 
corresponding subtype of the `sql:TypedValue` such as `sql:Varchar`, `sql:Char`, `sql:Integer`, etc., when you need to 
provide more details such as the exact SQL type of the parameter.

```ballerina
sql:VarcharValue name = new ("James");
sql:IntegerValue age = new (10);

sql:ParameterizedQuery query = `INSERT INTO student(age, name)
                                values (${age}, ${name})`;
sql:ExecutionResult ret = check dbClient->execute(query);
```

#### Inserting Data With Auto-generated Keys

This example demonstrates inserting data while returning the auto-generated keys. It achieves this by using the 
`execute` remote function to execute the `INSERT` statement.

```ballerina
int age = 31;
string name = "Kate";

sql:ParameterizedQuery query = `INSERT INTO student(age, name)
                                values (${age}, ${name})`;
sql:ExecutionResultret = check dbClient->execute(query);
//Number of rows affected by the execution of the query.
int? count = ret.affectedRowCount;
//The integer or string generated by the database in response to a query execution.
string|int? generatedKey = ret.lastInsertId;
}
```

#### Querying Data

This sample shows three examples to demonstrate the different usages of the `query` operation to query the
database table and obtain the results. 

This example demonstrates querying data from a table in a database. 
First, a type is created to represent the returned result set. Note the mapping of the database column 
to the returned record's property is case-insensitive (i.e., the `ID` column in the result can be mapped to the `id` 
property in the record). Next, the `SELECT` query is executed via the `query` remote function of the client by passing that 
result set type. Once the query is executed, each data record can be retrieved by looping the result set. The `stream` 
returned by the select operation holds a pointer to the actual data in the database and it loads data from the table 
only when it is accessed. This stream can be iterated only once. 

```ballerina
// Define a type to represent the results.
type Student record {
    int id;
    int age;
    string name;
};

// Select the data from the database table. The query parameters are passed 
// directly. Similar to the `execute` examples, parameters can be passed as
// sub types of `sql:TypedValue` as well.
int id = 10;
int age = 12;
sql:ParameterizedQuery query = `SELECT * FROM students
                                WHERE id < ${id} AND age > ${age}`;
stream<Student, sql:Error> resultStream = 
        <stream<Student, sql:Error>> dbClient->query(query, Student);

// Iterating the returned table.
error? e = resultStream.forEach(function(Student student) {
   //Can perform any operations using 'student' and can access any fields in the returned record of type Student.
});
```

Defining the return type is optional and you can query the database without providing the result type. Hence, 
the above example can be modified as follows with an open record type as the return type. The property name in the open record 
type will be the same as how the column is defined in the database. 

```ballerina
// Select the data from the database table. The query parameters are passed 
// directly. Similar to the `execute` examples, parameters can be passed as 
// sub types of `sql:TypedValue` as well.
int id = 10;
int age = 12;
sql:ParameterizedQuery query = `SELECT * FROM students
                                WHERE id < ${id} AND age > ${age}`;
stream<record{}, sql:Error> resultStream = dbClient->query(query);

// Iterating the returned table.
error? e = resultStream.forEach(function(record{} student) {
    //Can perform any operations using the 'student' and can access any fields in the returned record.
});
```

There are situations in which you may not want to iterate through the database and in that case, you may decide
to only use the `next()` operation in the result `stream` and retrieve the first record. In such cases, the returned
result stream will not be closed, and you have to explicitly invoke the `close` operation on the 
`sql:Client` to release the connection resources and avoid a connection leak as shown below.

```ballerina
stream<record{}, sql:Error> resultStream = 
            dbClient->query("SELECT count(*) as total FROM students");

record {|record {} value;|}|error? result = resultStream.next();

if result is record {|record {} value;|} {
    // A valid result is returned.
} else if result is error {
    // An error is returned as the result.
} else {
    // Student table must be empty.
}

error? e = resultStream.close();
```

#### Updating Data

This example demonstrates modifying data by executing an `UPDATE` statement via the `execute` remote function of 
the client.

```ballerina
int age = 23;
sql:ParameterizedQuery query = `UPDATE students SET name = 'John' 
                                WHERE age = ${age}`;
sql:ExecutionResult|sql:Error ret = check dbClient->execute(query);
```

#### Deleting Data

This example demonstrates deleting data by executing a `DELETE` statement via the `execute` remote function of 
the client.

```ballerina
string name = "John";
sql:ParameterizedQuery query = `DELETE from students WHERE name = ${name}`;
sql:ExecutionResult|sql:Error ret = check dbClient->execute(query);
```

#### Batch Updating Data

This example demonstrates how to insert multiple records with a single `INSERT` statement that is executed via the 
`batchExecute` remote function of the client. This is done by creating a `table` with multiple records and 
parameterized SQL query as same as the above `execute` operations.

```ballerina
// Create the table with the records that need to be inserted.
var data = [
  { name: "John", age: 25  },
  { name: "Peter", age: 24 },
  { name: "jane", age: 22 }
];

// Do the batch update by passing the batches.
sql:ParameterizedQuery[] batch = from var row in data
                                 select `INSERT INTO students ('name', 'age')
                                 VALUES (${row.name}, ${row.age})`;
sql:ExecutionResult[] ret = check dbClient->batchExecute(batch);
```

#### Execute SQL Stored Procedures

This example demonstrates how to execute a stored procedure with a single `INSERT` statement that is executed via the 
`call` remote function of the client.

```ballerina
int uid = 10;
sql:IntegerOutParameter insertId = new;

sql:ProcedureCallResult|sql:Error ret = dbClient->call(`call InsertPerson(${uid}, ${insertId})`);
if ret is error {
    //An error returned.
} else {
    stream<record{}, sql:Error>? resultStr = ret.queryResult;
    if resultStr is stream<record{}, sql:Error> {
        sql:Error? e = resultStr.forEach(function(record{} result) {
        //can perform operations using 'result'.
      });
    }
    check ret.close();
}
```
Note that you have to invoke the close operation explicitly on the `sql:ProcedureCallResult` to release the connection resources and avoid a connection leak as shown above.

>**Note:** The default thread pool size used in Ballerina is: [the number of processors available * 2] . You can configure
the thread pool size by using the `BALLERINA_MAX_POOL_SIZE` environment variable.


Represents an error originating from application-level causes.


ApplicationError

Defines the common error type for the module.


generateApplicationErrorStream

message

getGlobalConnectionPool

ConnectionPool

Queries the database with the query provided by the user, and returns the result as a stream.



query

The query which needs to be executed as a `string` or an `sql:ParameterizedQuery` when the SQL query has
params to be passed in


sqlQuery

The `typedesc` of the record that should be returned as a result. If this is not provided, the default
column names of the query result set will be used for the record attributes


rowType

Stream of records in the type of `rowType`


Executes the provided DDL or DML SQL query and returns a summary of the execution.



execute

The DDL or DML queries such as `INSERT`, `DELETE`, `UPDATE`, etc. as a `string`,
or an `sql:ParameterizedQuery` when the query has params to be passed in


Summary of the SQL update query as an `sql:ExecutionResult` or an `sql:Error`
if any error occurred when executing the query


Executes a batch of provided parameterized DDL or DML SQL queries
and returns the summary of the execution.



batchExecute

The DDL or DML queries such as `INSERT`,`DELETE`, `UPDATE`, etc. as an `sql:ParameterizedQuery`
with an array of values passed in


sqlQueries

Summary of the executed SQL queries as an `sql:ExecutionResult[]`, which includes details such as
the `affectedRowCount`, and `lastInsertId`. If one of the commands in the batch fails, this function
will return an `sql:BatchExecuteError`. However, the driver may or may not continue to process the
remaining commands in the batch after a failure. The summary of the executed queries in case of an error
can be accessed as `(<sql:BatchExecuteError> result).detail()?.executionResults`


Executes a SQL stored procedure and returns the result as stream and execution summary.



call

The query to execute the SQL stored procedure


The array of `typedesc` of the records that should be returned as a result. If this is not provided,
the default column names of the query result set will be used for the record attributes


rowTypes

Summary of the execution is returned in an `sql:ProcedureCallResult`, or an `sql:Error`


Client

The object type that is used as a structure to define a custom class with custom
implementations for nextResult and getNextQueryResult in the connector modules.



nextResult

iterator

callResult

Represents all OUT parameters used in SQL stored procedure call.


OutParameter

Represents Parameterized Call SQL Statement.



strings

insertions

RawTemplate

The separated parts of the sql call query


ParameterizedCallQuery

This module provides the common interface and functionality to interact with a database. The corresponding database

Class: NVarcharArrayValue

Fields