Yogyakarta, 10–13 November 2025 — The Graduate School of Yogyakarta State University (GS UNY) organized a four-day SQL Training Program to strengthen data analytics capacity and technical competence in database management. The training was delivered by Ir. Oktaf Agni Dhewa, S.Si., M.Cs., and attended by participants from PT BPD DIY. It was designed progressively to guide participants from foundational understanding to intermediate and advanced operational skills in SQL.

Day 1: Advanced Filters & JOIN Fundamentals
Participants learned advanced filter operators such as LIKE, IN, BETWEEN, and IS NULL for precise and efficient data searching. The instructor highlighted how wildcard operators, value ranges, and NULL handling affect query performance.
The session continued with JOIN fundamentals, including understanding primary keys (PK), foreign keys (FK), and reconstructing normalized database structures using INNER JOIN. Participants practiced identifying inter-table relationships and constructing cross-entity queries using real cases from the db_tokomaju database.

Day 2: Multi-table JOIN & Aggregation JOIN
Topics included advanced table combinations through LEFT JOIN, RIGHT JOIN, and multi-table JOIN involving up to four tables. Participants learned proper placement of conditions in ON and WHERE clauses to maintain correct outer join behavior.
They then practiced aggregations combined with JOIN—such as counting products per category, calculating customer spending totals, and analyzing revenue per category—integrating GROUP BY and aggregate functions into business analysis.

Day 3: Subqueries and Nested Query Construction
The third day introduced subqueries as a technique for running queries within queries. Topics covered scalar, multi-row, multi-column, correlated, and non-correlated subqueries.
Participants applied subqueries in SELECT, WHERE, and FROM clauses, including creating derived tables for complex calculations such as average revenue per order and multi-layered data searches. Emphasis was placed on execution efficiency and its impact on the database system.

Day 4: Data Manipulation Language (DML)
Participants practiced using transactions (START TRANSACTION; COMMIT; ROLLBACK) to maintain data security during modifications. Case studies included product data correction, mass discount updates, canceled order deletions, and customer archive management.

The session closed with a simulation combining JOIN, subqueries, and DML to solve real-world database challenges.

Through this four-day program, GS UNY reaffirmed its commitment to developing competent human resources in modern database management—skilled in cross-entity analysis using JOIN and subqueries and capable of executing secure, efficient data manipulation. Participants are expected to apply these skills within their respective institutions to enhance service quality and data-driven decision-making.