Writing SQL

Writing SQL for RDBMS Integrations

RDBMS exports and imports use SQL queries to read from and write to relational databases. Queries are Handlebars templates -- the platform evaluates expressions like {{{record.fieldName}}} at runtime, then executes the resulting SQL against the connected database.

This skill covers what SQL to write and how to write it. For which adaptor type to use, connection setup, and queryType selection, see the related skills below.

Quick Reference

Context decision matrix

Key syntax rules

1. Always use record. prefix (AFE 2.0). Never bare fieldName or data.fieldName.
2. Prefer triple braces {{{ }}} for values in SQL. Double braces {{ }} auto-wrap values in single quotes in RDBMS context -- this silently corrupts numeric values and breaks SQL syntax.
3. Add your own quotes for strings: '{{{record.name}}}'. Triple braces give you full control.
4. No quotes for numbers: {{{record.quantity}}}.
5. Import query is an array of strings, not a single string: ["INSERT INTO ..."].
6. Nested fields use dot notation: {{{record.address.city}}}.

Related skills

• configuring-exports > RDBMS -- adaptorType, delta/once mode, export-level config
• configuring-imports > RDBMS -- queryType decision tree, bulkInsert/bulkLoad config
• writing-handlebars -- full Handlebars syntax, helpers, block expressions
• configuring-connections > RDBMS -- database connection setup

Schema reference

• rdbms-export.yml -- export query and once fields
• rdbms-import.yml -- import query, queryType, bulkInsert, bulkLoad fields

How to Write a SQL Query

1. Discover the schema

Query the live database to find tables and columns before writing SQL:

celigo metadata types <connectionId>                    # List tables
celigo metadata fields <connectionId> <tableName>       # List columns and types

For Snowflake, use fully qualified names: database.schema.table.

2. Determine the query pattern

Exports -- what kind of data fetch?

Imports -- what kind of write operation?

3. Write the SQL

Follow the database-specific dialect patterns below. Use {{{record.fieldName}}} for runtime values.

4. Test the query

# Test an export query -- invoke returns real data
celigo exports invoke <exportId>

# Test an import -- submit test records
echo '[{"name":"test","email":"test@example.com"}]' | celigo imports invoke <importId>

Export Query Patterns

Standard SELECT

SELECT id, name, email, status
FROM customers
WHERE status = 'ACTIVE'
ORDER BY id

Delta export (incremental)

Use {{lastExportDateTime}} (platform-injected, not from a record). The token resolves to the timestamp of the last successful export run.

SELECT id, name, email, updated_at
FROM customers
WHERE updated_at > '{{lastExportDateTime}}'
ORDER BY updated_at ASC

For databases that need specific timestamp formats:

-- Snowflake
WHERE updated_at > TO_TIMESTAMP('{{lastExportDateTime}}', 'YYYY-MM-DD HH24:MI:SS')

-- MySQL
WHERE updated_at > STR_TO_DATE('{{lastExportDateTime}}', '%Y-%m-%d %H:%i:%s')

-- PostgreSQL
WHERE updated_at > '{{lastExportDateTime}}'::timestamp

Once export (mark-as-processed)

Two queries work together. The export rdbms.query fetches unprocessed records; rdbms.once.query marks each one after successful export.

{
  "type": "once",
  "rdbms": {
    "query": "SELECT id, name, email FROM orders WHERE exported = false",
    "once": {
      "query": "UPDATE orders SET exported = true WHERE id = {{{record.id}}}"
    }
  }
}

JOINs

SELECT o.id, o.order_date, c.name AS customer_name, c.email,
       p.product_name, oi.quantity, oi.unit_price
FROM orders o
JOIN customers c ON o.customer_id = c.id
JOIN order_items oi ON o.id = oi.order_id
JOIN products p ON oi.product_id = p.id
WHERE o.status = 'SHIPPED'
  AND o.order_date > '{{lastExportDateTime}}'

Aggregations

SELECT customer_id, COUNT(*) AS order_count, SUM(total) AS lifetime_value
FROM orders
WHERE status IN ('COMPLETED', 'SHIPPED')
GROUP BY customer_id
HAVING SUM(total) > 1000

Import Query Patterns

All import queries use {{{record.fieldName}}} to inject values from incoming records. The query field is an array of strings.

INSERT (per_record)

{
  "rdbms": {
    "queryType": ["per_record"],
    "query": ["INSERT INTO customers (name, email, phone) VALUES ('{{{record.name}}}', '{{{record.email}}}', '{{{record.phone}}}')"]
  }
}

UPDATE (per_record)

{
  "rdbms": {
    "queryType": ["per_record"],
    "query": ["UPDATE customers SET name = '{{{record.name}}}', email = '{{{record.email}}}' WHERE id = {{{record.id}}}"]
  }
}

UPSERT -- database-specific

MySQL (ON DUPLICATE KEY UPDATE):

{
  "rdbms": {
    "queryType": ["per_record"],
    "query": ["INSERT INTO customers (id, name, email) VALUES ({{{record.id}}}, '{{{record.name}}}', '{{{record.email}}}') ON DUPLICATE KEY UPDATE name = '{{{record.name}}}', email = '{{{record.email}}}'"]
  }
}

PostgreSQL (ON CONFLICT):

{
  "rdbms": {
    "queryType": ["per_record"],
    "query": ["INSERT INTO customers (id, name, email) VALUES ({{{record.id}}}, '{{{record.name}}}', '{{{record.email}}}') ON CONFLICT (id) DO UPDATE SET name = EXCLUDED.name, email = EXCLUDED.email"]
  }
}

Snowflake (MERGE):

{
  "rdbms": {
    "queryType": ["per_record"],
    "query": ["MERGE INTO customers AS t USING (SELECT {{{record.id}}} AS id, '{{{record.name}}}' AS name, '{{{record.email}}}' AS email) AS s ON t.id = s.id WHEN MATCHED THEN UPDATE SET t.name = s.name, t.email = s.email WHEN NOT MATCHED THEN INSERT (id, name, email) VALUES (s.id, s.name, s.email)"]
  }
}

SQL Server (MERGE):

{
  "rdbms": {
    "queryType": ["per_record"],
    "query": ["MERGE INTO customers AS t USING (SELECT {{{record.id}}} AS id, '{{{record.name}}}' AS name, '{{{record.email}}}' AS email) AS s ON t.id = s.id WHEN MATCHED THEN UPDATE SET t.name = s.name, t.email = s.email WHEN NOT MATCHED THEN INSERT (id, name, email) VALUES (s.id, s.name, s.email);"]
  }
}

Multiple statements (per_record)

When you need to run multiple SQL statements per record, add them as separate array elements:

{
  "rdbms": {
    "queryType": ["per_record"],
    "query": [
      "INSERT INTO orders (id, customer_id, total) VALUES ({{{record.orderId}}}, {{{record.customerId}}}, {{{record.total}}})",
      "UPDATE customers SET last_order_date = CURRENT_TIMESTAMP WHERE id = {{{record.customerId}}}"
    ]
  }
}

Bulk insert (no SQL needed)

For pure INSERTs with no duplicate checking, use bulkInsert -- the platform generates the SQL:

{
  "rdbms": {
    "queryType": ["bulk_insert"],
    "bulkInsert": {
      "tableName": "customers",
      "batchSize": "1000"
    }
  }
}

Column mapping comes from mappings[] on the import (Mapper 2.0). Each mapping's generate value must match a column name in the target table.

Bulk load with auto-generated MERGE

For high-volume upsert on Snowflake or Azure Synapse, use bulkLoad with primaryKeys:

{
  "rdbms": {
    "queryType": ["bulk_load"],
    "bulkLoad": {
      "tableName": "WAREHOUSE.PUBLIC.CUSTOMERS",
      "primaryKeys": "id"
    }
  }
}

The platform stages data into a temporary table, then auto-generates a MERGE using the primary keys. For composite keys: "primaryKeys": "order_id,product_id".

Bulk load with custom merge

When the auto-generated MERGE isn't sufficient (conditional updates, ignore-existing, multi-table ops), override it:

{
  "rdbms": {
    "queryType": ["bulk_load"],
    "bulkLoad": {
      "tableName": "WAREHOUSE.PUBLIC.CUSTOMERS",
      "primaryKeys": "id",
      "overrideMergeQuery": true
    }
  }
}

The custom SQL goes in the rdbms.query field (yes, even with bulkLoad). Reference the staging table via {{import.rdbms.bulkLoad.preMergeTemporaryTable}}:

MERGE INTO WAREHOUSE.PUBLIC.CUSTOMERS AS t
USING {{import.rdbms.bulkLoad.preMergeTemporaryTable}} AS s
ON t.id = s.id
WHEN MATCHED AND s.updated_at > t.updated_at THEN
  UPDATE SET t.name = s.name, t.email = s.email, t.updated_at = s.updated_at
WHEN NOT MATCHED THEN
  INSERT (id, name, email, updated_at) VALUES (s.id, s.name, s.email, s.updated_at)

per_page batch operations

per_page gives you the entire page of records as batch_of_records. Use {{#each}} to iterate:

{
  "rdbms": {
    "queryType": ["per_page"],
    "query": ["INSERT INTO customers (name, email) VALUES {{#each batch_of_records}}('{{{record.name}}}', '{{{record.email}}}'){{#unless @last}},{{/unless}}{{/each}}"]
  }
}

Dialect Patterns

Snowflake

-- Fully qualified table names (required unless connection sets default schema)
SELECT * FROM MY_DATABASE.MY_SCHEMA.MY_TABLE

-- FLATTEN for semi-structured data (VARIANT columns)
SELECT f.value:name::STRING AS name, f.value:email::STRING AS email
FROM MY_TABLE, LATERAL FLATTEN(input => MY_TABLE.json_column) f

-- QUALIFY for window function filtering
SELECT * FROM orders
QUALIFY ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY order_date DESC) = 1

-- Timestamp handling
WHERE updated_at > TO_TIMESTAMP('{{lastExportDateTime}}', 'YYYY-MM-DD"T"HH24:MI:SS')

-- Case: Snowflake uppercases unquoted identifiers. Use double quotes to preserve case
SELECT "camelCaseColumn" FROM "MixedCaseTable"

PostgreSQL

-- JSONB operators
SELECT data->>'name' AS name, data->'address'->>'city' AS city
FROM customers WHERE data @> '{"active": true}'

-- ILIKE for case-insensitive matching
SELECT * FROM products WHERE name ILIKE '%widget%'

-- ON CONFLICT for upsert
INSERT INTO customers (id, name, email) VALUES ({{{record.id}}}, '{{{record.name}}}', '{{{record.email}}}')
ON CONFLICT (id) DO UPDATE SET name = EXCLUDED.name, email = EXCLUDED.email

-- Array operations
SELECT * FROM users WHERE 'admin' = ANY(roles)

-- CTEs
WITH recent_orders AS (
  SELECT * FROM orders WHERE order_date > '{{lastExportDateTime}}'
)
SELECT c.name, r.total FROM customers c JOIN recent_orders r ON c.id = r.customer_id

MySQL / MariaDB

-- ON DUPLICATE KEY UPDATE for upsert
INSERT INTO customers (id, name, email)
VALUES ({{{record.id}}}, '{{{record.name}}}', '{{{record.email}}}')
ON DUPLICATE KEY UPDATE name = VALUES(name), email = VALUES(email)

-- JSON_EXTRACT for JSON columns
SELECT JSON_EXTRACT(data, '$.name') AS name FROM customers

-- GROUP_CONCAT for string aggregation
SELECT customer_id, GROUP_CONCAT(product_name SEPARATOR ', ') AS products
FROM order_items GROUP BY customer_id

-- IFNULL for null handling
SELECT IFNULL(middle_name, '') AS middle_name FROM users

-- Timestamp formatting
WHERE updated_at > STR_TO_DATE('{{lastExportDateTime}}', '%Y-%m-%d %H:%i:%s')

SQL Server / Azure Synapse

-- MERGE with required semicolon terminator
MERGE INTO customers AS t
USING (SELECT {{{record.id}}} AS id, '{{{record.name}}}' AS name) AS s
ON t.id = s.id
WHEN MATCHED THEN UPDATE SET t.name = s.name
WHEN NOT MATCHED THEN INSERT (id, name) VALUES (s.id, s.name);

-- TOP instead of LIMIT
SELECT TOP 100 * FROM orders ORDER BY order_date DESC

-- STRING_AGG for string aggregation (SQL Server 2017+)
SELECT customer_id, STRING_AGG(product_name, ', ') AS products
FROM order_items GROUP BY customer_id

-- CROSS APPLY for row-valued functions
SELECT c.name, o.total FROM customers c
CROSS APPLY (SELECT TOP 1 * FROM orders WHERE customer_id = c.id ORDER BY order_date DESC) o

-- Bracket identifiers for reserved words or special characters
SELECT [order], [name] FROM [my-table]

Oracle

-- NVL for null handling
SELECT NVL(middle_name, '') AS middle_name FROM users

-- ROWNUM for limiting results (pre-12c)
SELECT * FROM (SELECT * FROM orders ORDER BY order_date DESC) WHERE ROWNUM <= 100

-- FETCH FIRST for limiting results (12c+)
SELECT * FROM orders ORDER BY order_date DESC FETCH FIRST 100 ROWS ONLY

-- LISTAGG for string aggregation
SELECT customer_id, LISTAGG(product_name, ', ') WITHIN GROUP (ORDER BY product_name)
FROM order_items GROUP BY customer_id

-- MERGE
MERGE INTO customers t USING (SELECT {{{record.id}}} AS id, '{{{record.name}}}' AS name FROM dual) s
ON (t.id = s.id)
WHEN MATCHED THEN UPDATE SET t.name = s.name
WHEN NOT MATCHED THEN INSERT (id, name) VALUES (s.id, s.name)

BigQuery

-- Backtick identifiers
SELECT * FROM `project.dataset.table`

-- UNNEST for array columns
SELECT * FROM `orders`, UNNEST(items) AS item

-- STRUCT access
SELECT address.city, address.state FROM customers

-- SAFE_DIVIDE to avoid division by zero
SELECT SAFE_DIVIDE(revenue, orders) AS avg_order_value FROM metrics

-- Timestamp handling
WHERE updated_at > TIMESTAMP('{{lastExportDateTime}}')

Redshift

-- PostgreSQL-based syntax
SELECT * FROM orders WHERE status = 'ACTIVE'

-- LISTAGG for string aggregation
SELECT customer_id, LISTAGG(product_name, ', ') WITHIN GROUP (ORDER BY product_name)
FROM order_items GROUP BY customer_id

-- COPY-oriented -- bulk_load uses Redshift COPY under the hood
-- For custom merge logic, use overrideMergeQuery with staging table reference

Pre-Submit Checklist

Export queries

• SELECT query is syntactically valid for the target database dialect
• Delta uses {{lastExportDateTime}} in the query, NOT a delta object inside rdbms
• Once export has both queries -- rdbms.query for SELECT and rdbms.once.query for UPDATE
• Table and column names exist -- verify with celigo metadata types/fields <connectionId>
• Snowflake uses fully qualified names -- database.schema.table unless the connection sets defaults

Import queries

• query is an array of strings -- ["INSERT INTO ..."], not "INSERT INTO ..."
• queryType matches the operation -- ["per_record"] for UPDATE/UPSERT, ["bulk_insert"] for pure INSERT, ["bulk_load"] for high-volume
• All {{{record.fieldName}}} paths match incoming data -- invoke the upstream export to verify field names
• Strings are quoted, numbers are not -- '{{{record.name}}}' vs {{{record.id}}}
• Uses record. prefix -- not bare fieldName or data.fieldName
• Uses triple braces {{{ }}} -- double braces auto-wrap in quotes, breaking numeric values and SQL syntax
• bulkInsert/bulkLoad not set alongside query -- these are mutually exclusive with the query field (except overrideMergeQuery)

Cross-resource

• Connection type is RDBMS -- type on the connection matches one of: mysql, mariadb, postgresql, mssql, azuresynapse, oracle, snowflake, bigquery, redshift
• SQL dialect matches the database -- MERGE syntax differs between Snowflake, SQL Server, Oracle, PostgreSQL

Gotchas

1. Double braces auto-format in RDBMS. {{record.name}} outputs 'value' (wrapped in quotes). {{{record.name}}} outputs value (raw). Use triple braces and add your own quotes for strings -- this gives you control and avoids double-quoting or broken numeric values.
2. Import query must be an array. "query": "INSERT INTO ..." fails silently or throws a Cast error. Always use ["INSERT INTO ..."].
3. queryType values are specific. Use ["per_record"], ["bulk_insert"], ["per_page"], ["bulk_load"]. Do NOT use ["INSERT"] or ["UPDATE"] as standalone values.
4. Snowflake rejects legacy queryType values on PUT. insert/update may work on POST but fail on PUT. Use per_record or bulk_insert from the start.
5. Missing record. prefix produces empty values. {{{name}}} resolves to nothing. Always use {{{record.name}}}.
6. Snowflake requires fully qualified table names. database.schema.table unless the connection sets a default schema. Unqualified names fail silently or hit the wrong table.
7. per_page has a different Handlebars context. The context is batch_of_records, not a single record. Use {{#each batch_of_records}}...{{{record.fieldName}}}...{{/each}}.
8. bulkLoad.overrideMergeQuery references a staging table. Use {{import.rdbms.bulkLoad.preMergeTemporaryTable}} -- not the target table name.
9. SQL Server MERGE requires a semicolon terminator. Missing ; at the end causes syntax errors.
10. once.query runs per record, not per batch. The {{record.id}} in the once query refers to the current exported record. Don't write batch UPDATE statements here.
11. Don't put delta config inside rdbms. There's no rdbms.delta property. Delta is handled by embedding {{lastExportDateTime}} directly in the SQL query text.
12. NULL handling varies by dialect. Use NVL (Oracle), IFNULL (MySQL), COALESCE (standard/Snowflake/PostgreSQL/SQL Server). Don't assume one works everywhere.

Common Errors