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SQL Connector

Overview

Section titled “Overview”

The SQL connector writes data to relational databases.

Connector Type: SqlWriter

Supported Databases:

  • MySQL
  • PostgreSQL
  • SQL Server (MSSQL)

Configuration

Section titled “Configuration”

MySQL

Section titled “MySQL”
{
  "type": "SqlWriter",
  "config": {
    "connectionString": "user:password@tcp(localhost:3306)/database_name",
    "driver": "mysql",
    "table": "sensor_data",
    "writeAction": "Insert",
    "mode": "ColumnMapping",
    "columns": {
      "temperature": "temp_column",
      "pressure": "press_column",
      "timestamp": "ts_column"
    }
  }
}

PostgreSQL

Section titled “PostgreSQL”
{
  "type": "SqlWriter",
  "config": {
    "connectionString": "host=localhost port=5432 user=postgres password=pass dbname=mydb sslmode=disable",
    "driver": "postgres",
    "table": "measurements",
    "writeAction": "Insert",
    "mode": "ColumnMapping",
    "columns": {
      "temperature": "temperature",
      "humidity": "humidity"
    }
  }
}

SQL Server

Section titled “SQL Server”
{
  "type": "SqlWriter",
  "config": {
    "connectionString": "sqlserver://user:pass@localhost:1433?database=mydb",
    "driver": "sqlserver",
    "table": "sensor_readings",
    "writeAction": "Upsert",
    "mode": "ColumnMapping",
    "columns": {
      "sensor_id": "id",
      "value": "reading_value"
    }
  }
}

Configuration Parameters

Section titled “Configuration Parameters”
  • connectionString: Database-specific connection string
  • driver: Database driver (mysql, postgres, sqlserver)
  • table: Target table name
  • writeAction: Write operation (Insert, Update, Upsert)
  • mode: Mapping mode (ColumnMapping)
  • columns: Map payload keys to database columns

Write Actions

Section titled “Write Actions”

Insert

Section titled “Insert”

Add new rows:

{
  "writeAction": "Insert"
}

Update

Section titled “Update”

Update existing rows (requires WHERE condition):

{
  "writeAction": "Update"
}

Upsert

Section titled “Upsert”

Insert or update if exists:

{
  "writeAction": "Upsert"
}

Column Mapping

Section titled “Column Mapping”

Map Meddle payload keys to database columns:

{
  "columns": {
    "payload_key": "database_column",
    "temperature": "temp_celsius",
    "pressure": "pressure_bar",
    "timestamp": "recorded_at"
  }
}

Connection Strings

Section titled “Connection Strings”

MySQL

Section titled “MySQL”
user:password@tcp(host:port)/database?param=value

PostgreSQL

Section titled “PostgreSQL”
host=localhost port=5432 user=user password=pass dbname=db sslmode=disable

SQL Server

Section titled “SQL Server”
sqlserver://user:pass@host:port?database=db&param=value

Use Case: Production Data Logging

Section titled “Use Case: Production Data Logging”
{
  "type": "SqlWriter",
  "config": {
    "connectionString": "user:pass@tcp(mysql.local:3306)/production",
    "driver": "mysql",
    "table": "machine_logs",
    "writeAction": "Insert",
    "mode": "ColumnMapping",
    "columns": {
      "machine_id": "machine_id",
      "temperature": "temperature",
      "speed": "rpm",
      "status": "operational_status",
      "timestamp": "log_time"
    }
  }
}

Best Practices

Section titled “Best Practices”
  1. Create appropriate indexes on frequently queried columns
  2. Use Upsert for idempotent operations
  3. Ensure table schema matches column mappings
  4. Use connection pooling for high-throughput scenarios
  5. Monitor database performance and query execution times

Troubleshooting

Section titled “Troubleshooting”

Connection Failed

Section titled “Connection Failed”
  • Verify connection string format
  • Check database server is running
  • Verify credentials
  • Check firewall rules

Column Not Found

Section titled “Column Not Found”
  • Ensure column names in mapping match database schema
  • Check table exists
  • Verify case sensitivity
Section titled “Related Connectors”