MATLAB Database Toolbox Pushdown Architect

MATLAB Database Toolbox Pushdown Architect

Use when importing data from relational databases with MATLAB Database Toolbox's pushdown capabilities — offloading row filtering, column selection, duplicate exclusion, and joins to the database instead of processing in MATLAB.

When to Use This Skill

• Importing data from a database table or an SQL query as a MATLAB table
• Filtering rows from a database table or an SQL query
• Selecting specific columns from a database table or an SQL query
• Excluding duplicate rows in a database table or an SQL query
• Joining two database tables
• Combining joins with filtering or column selection
• User mentions keywords: import, sqlread, fetch, filter, rowfilter, join, sqlinnerjoin, sqlouterjoin, duplicates, databaseImportOptions, pushdown

When NOT to Use

• Writing/inserting data into a database — use sqlwrite/sqlupdate/execute patterns instead
• Data too large to fit in memory — use DatabaseDatastore + tall arrays or splitsqlquery
• Object-oriented reads with class mapping — use ORM (ormread with Mappable classes)
• MongoDB, Cassandra, or Neo4j queries — pushdown functions only work with relational databases

Critical Rules

Pushdown Strategy

• ALWAYS use sqlread for tables, fetch for SQL queries.
• ALWAYS use RowFilter to push row filtering to the database. NEVER import all rows and filter in MATLAB.
• ALWAYS use databaseImportOptions with SelectedVariableNames when only a subset of columns is needed.
• ALWAYS verify the connection with isopen(conn) before operations and call close(conn) when done.

Joins

• ALWAYS use sqlinnerjoin/sqlouterjoin for joining exactly 2 database tables.
• NEVER pass databaseImportOptions (opts) to sqlinnerjoin or sqlouterjoin — they do not accept it. Select columns in MATLAB after the join, or use fetch with explicit SQL.
• NEVER use pushdown joins for 3+ tables or joins with aggregation — use fetch with explicit SQL instead.

Function Reference

What Each Function Accepts

| Function | Accepts opts? | Accepts RowFilter? | Accepts MaxRows? | Column Selection |