Queries

Queries define the SQL statements you want to execute and monitor.

Purpose

Queries allow you to:

Define SQL statements to extract data from your databases
Use parameters for dynamic query values
Create multi-step query workflows
Reuse queries across multiple subscriptions
Monitor query execution history

Use Cases

Data Validation (Primary): Alert when data violates business rules or integrity constraints
Data Quality Checks: Detect NULL values, duplicates, orphaned records, invalid states
Business Rule Enforcement: Trigger alerts when data doesn’t meet expected criteria
Database Health (Secondary): Monitor database metrics for DBAs (table size, connections, performance)
Compliance Reporting: Generate audit reports on schedules

Creating a Simple Query

Step 1: Navigate to Queries

Log in to Semantico
Click Queries in the left navigation
Click Create New Query

Step 2: Fill Query Details

Field	Description	Required	Example
Name	Descriptive query name	Yes	`Daily Active Users`
Description	Purpose of this query	No	`Count users active in last 24 hours`
Store Results	Save execution results	No	✓ Checked

Step 3: Add Query Step

Every query has at least one step. Click Add Query Step:

Field	Description	Required	Example
Step Name	Name for this step	Yes	`Count Active Users`
Project	Database to query	Yes	Select your project
SQL Query	SQL statement	Yes	See examples below
Order	Execution order	Yes	1 (for first step)

Simple query example:

SELECT COUNT(*) as active_users
FROM users
WHERE last_login >= NOW() - INTERVAL '24 hours'

Step 4: Save Query

Click Save to create the query.

Query Examples

Monitor Table Growth

PostgreSQL:

SELECT
    schemaname,
    tablename,
    pg_size_pretty(pg_total_relation_size(schemaname||'.'||tablename)) AS size,
    pg_total_relation_size(schemaname||'.'||tablename) AS size_bytes
FROM pg_tables
WHERE schemaname = 'public'
ORDER BY size_bytes DESC
LIMIT 10

SQL Server:

SELECT
    t.NAME AS TableName,
    s.Name AS SchemaName,
    p.rows AS RowCount,
    CAST(ROUND((SUM(a.total_pages) * 8) / 1024.00, 2) AS NUMERIC(36, 2)) AS SizeMB
FROM sys.tables t
INNER JOIN sys.indexes i ON t.OBJECT_ID = i.object_id
INNER JOIN sys.partitions p ON i.object_id = p.OBJECT_ID AND i.index_id = p.index_id
INNER JOIN sys.allocation_units a ON p.partition_id = a.container_id
LEFT OUTER JOIN sys.schemas s ON t.schema_id = s.schema_id
WHERE t.is_ms_shipped = 0
GROUP BY t.Name, s.Name, p.Rows
ORDER BY SizeMB DESC

Check Database Connections

PostgreSQL:

SELECT
    datname,
    count(*) as connections,
    max(client_addr) as last_client
FROM pg_stat_activity
WHERE datname IS NOT NULL
GROUP BY datname
ORDER BY connections DESC

SQL Server:

SELECT
    DB_NAME(dbid) as DatabaseName,
    COUNT(dbid) as NumberOfConnections,
    loginame as LoginName
FROM sys.sysprocesses
WHERE dbid > 0
GROUP BY dbid, loginame
ORDER BY NumberOfConnections DESC

Monitor Query Performance

PostgreSQL (slow queries):

SELECT
    query,
    calls,
    mean_exec_time,
    max_exec_time
FROM pg_stat_statements
WHERE mean_exec_time > 1000  -- Queries slower than 1 second
ORDER BY mean_exec_time DESC
LIMIT 20

Data Validation Examples (Primary Use Case)

Check for NULL values in required fields:

SELECT
    id,
    email,
    username
FROM users
WHERE email IS NULL
   OR username IS NULL
   OR created_at IS NULL
-- Alert triggers if any rows returned

Detect orphaned records:

SELECT
    o.id,
    o.user_id,
    'Orphaned order - user not found' as issue
FROM orders o
LEFT JOIN users u ON o.user_id = u.id
WHERE u.id IS NULL
-- Alert if orphaned orders exist

Check for invalid state combinations:

SELECT
    id,
    status,
    payment_status
FROM orders
WHERE status = 'completed'
  AND payment_status != 'paid'
-- Alert if completed orders are not paid

Detect duplicate records:

SELECT
    email,
    COUNT(*) as duplicate_count
FROM users
GROUP BY email
HAVING COUNT(*) > 1
-- Alert if duplicate emails exist

Business rule violations:

SELECT
    id,
    total_amount,
    discount_amount
FROM orders
WHERE discount_amount > total_amount
-- Alert if discount exceeds total (invalid business rule)

Referential integrity checks:

SELECT
    p.id,
    p.category_id,
    'Invalid category reference' as issue
FROM products p
WHERE category_id NOT IN (SELECT id FROM categories)
-- Alert if products reference non-existent categories

Query Parameters

Queries can include dynamic parameters using `` syntax.

Query with parameter:

SELECT COUNT(*) as user_count
FROM users
WHERE created_at >= ''
  AND created_at < ''

When creating a subscription, you’ll provide values for start_date and end_date.

📚 Learn more about Query Parameters →

Multi-Step Queries

Create complex workflows by chaining multiple query steps.

Example: Cross-database data aggregation:

Step 1 - Query PostgreSQL database:

SELECT customer_id, SUM(amount) as total
FROM orders
WHERE created_at >= CURRENT_DATE
GROUP BY customer_id

Step 2 - Aggregate results:

SELECT
    COUNT(*) as customers_with_orders,
    SUM(total) as grand_total,
    AVG(total) as average_order
FROM @result1  -- References Step 1 results

📚 Learn more about Multi-Step Queries →

Managing Queries

View Queries

The Queries page shows:

Query name and description
Associated project
Number of subscriptions using this query
Last execution time
Actions (Edit, Delete, Preview, View History)

Edit Query

Click Edit (pencil icon) on the query row
Modify query details or SQL
Test changes with Preview Execution
Click Save

Tip: Use Preview Execution to test query changes before saving. This shows results without creating execution history.

Delete Query

Careful: Deleting a query will disable all subscriptions using it.

Click Delete (trash icon) on the query row
Review impact message (shows affected subscriptions)
Confirm deletion

Queries are archived (soft delete) and can be restored if needed.

Preview Query Execution

Test queries without scheduling:

Open your query
Click Preview Query Execution
Review results in table format
Check execution time
Verify data is as expected

Query Best Practices

Performance

DO:

✓ Use indexes on frequently queried columns
✓ Limit result sets with LIMIT or TOP
✓ Filter early with WHERE clauses
✓ Use appropriate data types
✓ Test performance on production-sized data

DON’T:

✗ Use SELECT * (specify columns)
✗ Query without indexes
✗ Use complex JOINs unnecessarily
✗ Return millions of rows
✗ Use cursors or loops

Security

DO:

✓ Use read-only database users
✓ Parameterize dynamic values
✓ Validate query results make sense
✓ Monitor execution history for anomalies

DON’T:

✗ Use admin/superuser accounts
✗ Include passwords or secrets in queries
✗ Allow SQL injection via parameters
✗ Query sensitive data unnecessarily

Reliability

DO:

✓ Set appropriate timeout values
✓ Handle NULL values in aggregations
✓ Use defensive SQL (COALESCE, NULLIF)
✓ Test edge cases (empty results, errors)

DON’T:

✗ Rely on unstable temp tables
✗ Use database-specific syntax if cross-db needed
✗ Forget to handle zero-row results
✗ Use non-deterministic functions without intent

Query Examples by Use Case

Application Monitoring

Error rate (last hour):

SELECT
    error_type,
    COUNT(*) as error_count,
    MAX(created_at) as last_error
FROM error_logs
WHERE created_at > NOW() - INTERVAL '1 hour'
GROUP BY error_type
ORDER BY error_count DESC

Slow API endpoints:

SELECT
    endpoint,
    AVG(response_time_ms) as avg_response,
    MAX(response_time_ms) as max_response,
    COUNT(*) as request_count
FROM api_logs
WHERE created_at > NOW() - INTERVAL '1 hour'
GROUP BY endpoint
HAVING AVG(response_time_ms) > 1000  -- Slower than 1 second
ORDER BY avg_response DESC

Database Health

Disk space usage (PostgreSQL):

SELECT
    pg_database.datname,
    pg_size_pretty(pg_database_size(pg_database.datname)) AS size
FROM pg_database
ORDER BY pg_database_size(pg_database.datname) DESC

Index health (PostgreSQL):

SELECT
    schemaname,
    tablename,
    indexname,
    idx_scan,
    idx_tup_read,
    idx_tup_fetch
FROM pg_stat_user_indexes
WHERE idx_scan = 0  -- Unused indexes
ORDER BY pg_relation_size(indexrelid) DESC

Scheduled Reporting Queries

Queries designed for reports delivered as CSV/Excel attachments:

Daily sales report (complete dataset):

SELECT
    p.product_name,
    p.category,
    o.order_date,
    o.customer_id,
    c.customer_name,
    o.quantity,
    o.unit_price,
    o.total_amount
FROM orders o
JOIN products p ON o.product_id = p.id
JOIN customers c ON o.customer_id = c.id
WHERE DATE(o.created_at) = CURRENT_DATE - INTERVAL '1 day'
ORDER BY o.total_amount DESC
-- Full results sent as CSV attachment for Excel analysis

Weekly user activity report:

SELECT
    u.username,
    u.email,
    COUNT(a.id) as login_count,
    MAX(a.created_at) as last_login,
    SUM(a.duration_minutes) as total_minutes
FROM users u
LEFT JOIN activity_logs a ON u.id = a.user_id
    AND a.created_at >= CURRENT_DATE - INTERVAL '7 days'
GROUP BY u.id, u.username, u.email
ORDER BY login_count DESC
-- Delivered Monday mornings as CSV for management review

Monthly financial summary:

SELECT
    DATE_TRUNC('month', created_at) as month,
    category,
    COUNT(*) as transaction_count,
    SUM(amount) as total_amount,
    AVG(amount) as average_amount,
    MIN(amount) as min_amount,
    MAX(amount) as max_amount
FROM transactions
WHERE created_at >= DATE_TRUNC('month', CURRENT_DATE - INTERVAL '1 month')
  AND created_at < DATE_TRUNC('month', CURRENT_DATE)
GROUP BY DATE_TRUNC('month', created_at), category
ORDER BY category
-- Delivered first day of month with complete data for analysis

Reporting Power: These queries return complete datasets that are delivered as CSV attachments. Recipients can open them directly in Excel for pivot tables, charts, and further analysis without needing database access.

Troubleshooting

Query Syntax Errors

Test in database client first:

# PostgreSQL
psql -h host -U user -d database -c "SELECT COUNT(*) FROM users"

# SQL Server
sqlcmd -S server -U user -P password -d database -Q "SELECT COUNT(*) FROM users"

# MySQL
mysql -h host -u user -p database -e "SELECT COUNT(*) FROM users"

Query Timeout

If queries time out:

Check query execution plan for performance issues
Add indexes to improve performance
Increase timeout in subscription settings
Simplify query or reduce result set

Permission Errors

Verify user has SELECT permission:

-- PostgreSQL
SELECT grantee, table_schema, table_name, privilege_type
FROM information_schema.table_privileges
WHERE grantee = 'your_user';

Multi-Step Queries - Chain multiple queries
Query Parameters - Use dynamic parameters
Subscriptions - Schedule query execution
Projects - Database connection management

Queries

Purpose

Use Cases

Creating a Simple Query

Step 1: Navigate to Queries

Step 2: Fill Query Details

Step 3: Add Query Step

Step 4: Save Query

Query Examples

Monitor Table Growth

Check Database Connections

Monitor Query Performance

Data Validation Examples (Primary Use Case)

Query Parameters

Multi-Step Queries

Managing Queries

View Queries

Edit Query

Delete Query

Preview Query Execution

Query Best Practices

Performance

Security

Reliability

Query Examples by Use Case

Application Monitoring

Database Health

Scheduled Reporting Queries

Troubleshooting

Query Syntax Errors

Query Timeout

Permission Errors

Related Documentation