MATLAB Database Export Architect

Use when writing data to relational databases, executing SQL statements, managing transactions, running stored procedures, or using SQL prepared statements. Covers all Database Toolbox operations that modify the database.

When to Use This Skill

• Writing/inserting MATLAB data into a database table
• Updating existing rows in a database table
• Deleting data from a database
• Executing arbitrary SQL statements (DDL, DML)
• Running stored procedures or custom database functions
• Managing transactions (commit/rollback)
• Using SQL prepared statements for parameterized queries
• Creating or altering database table structures
• User mentions keywords: write, export, insert, sqlwrite, sqlupdate, update, delete, execute, stored procedure, runstoredprocedure, transaction, commit, rollback, DDL, CREATE TABLE, ALTER, prepared statement, bulk insert

When NOT to Use

• Reading/importing data from a database — use sqlread/fetch with RowFilter and databaseImportOptions
• Object-oriented writes with class mapping — use ORM (ormwrite/ormupdate with Mappable classes)
• MongoDB, Cassandra, or Neo4j writes — these have their own document/graph-specific write interfaces
• Large data that doesn't fit in memory — use DatabaseDatastore + chunked processing for reads, or chunked sqlwrite loops for writes

Critical Rules

Credential Security

• NEVER hardcode passwords or credentials in generated code.
• ALWAYS use setSecret / getSecret (R2024a+) for credential storage.

Database Connection

• ALWAYS establish and verify a connection before any export operation. Check isopen(conn) after connecting.
• ALWAYS close connections with close(conn) when done.

Transaction Safety

• ALWAYS set AutoCommit to off when using commit / rollback for transaction control.
• ALWAYS wrap multi-statement operations in a transaction when atomicity is required.
• ALWAYS use rollback in error-handling blocks to undo partial changes on failure.

Decision Framework

`execute` vs `runstoredprocedure`: Use runstoredprocedure when you need typed output arguments. Use execute with CALL for simple invocation or when you only need result sets.

Function Reference

Edge Cases

• NULL values: MATLAB missing, NaN, or empty "" map to SQL NULL in sqlwrite
• Type mismatches: Ensure MATLAB column types match DB column types (e.g., int32 not double for INTEGER columns)
• Auto-increment PKs: Omit the auto-increment column from the MATLAB table before calling sqlwrite

Core Concepts

See knowledge cards for detailed usage and examples:

• Insert and update data: reference/cards/sqlwrite-sqlupdate.md
• Execute SQL and stored procedures: reference/cards/execute-storedproc.md
• Transaction management: reference/cards/transactions.md
• Prepared statements (JDBC only): reference/cards/prepared-statements.md

Complete Examples

See knowledge cards for complete examples:

• Insert computed results: reference/cards/sqlwrite-sqlupdate.md
• Atomic multi-table update with transaction: reference/cards/transactions.md
• Parameterized insert with prepared statement: reference/cards/prepared-statements.md

Common Mistakes

% INCORRECT — inserting rows one at a time in a loop (very slow)
for i = 1:height(data)
    sqlwrite(conn, "orders", data(i,:));
end

% CORRECT — batch insert the entire table at once
sqlwrite(conn, "orders", data);

% INCORRECT — no transaction control for multi-table writes
sqlwrite(conn, "orders", orderData);
sqlwrite(conn, "order_items", itemData);  % if this fails, orders are orphaned

% CORRECT — use transaction control for atomic multi-table writes
conn.AutoCommit = 'off';
try
    sqlwrite(conn, "orders", orderData);
    sqlwrite(conn, "order_items", itemData);
    commit(conn);
catch ME
    rollback(conn);
    conn.AutoCommit = 'on'; %#ok<NASGU> restore before rethrowing
    rethrow(ME);
end
conn.AutoCommit = 'on';

% INCORRECT — including auto-increment column in sqlwrite
data = table(1, "Widget", 9.99, VariableNames=["ID", "Name", "Price"]);
sqlwrite(conn, "products", data);  % Error if ID is auto-increment

% CORRECT — omit auto-increment column
data = table("Widget", 9.99, VariableNames=["Name", "Price"]);
sqlwrite(conn, "products", data);

Best Practices

• ALWAYS use sqlwrite for inserting MATLAB tables — it handles type mapping automatically.
• ALWAYS prefer sqlupdate (R2023a+) over raw SQL UPDATE — it uses rowfilter for type-safe filtering.
• ALWAYS close connections with close(conn) when done.
• Prefer transactions (commit/rollback) for multi-statement operations requiring atomicity.
• For very large inserts, chunk the MATLAB table manually in a loop to avoid memory issues.
• Use prepared statements for repeated parameterized operations — they improve performance and prevent SQL injection.
• Prepared statements are JDBC only — not available for ODBC or native connections.
• runstoredprocedure is JDBC/ODBC only (database() connections) — not available for native connections (sqlite, postgresql, mysql, duckdb). Use execute with a CALL statement instead.

Common Patterns

Pattern 1: Insert-Verify

sqlwrite(conn, "myTable", data);
result = sqlread(conn, "myTable");
disp("Rows after insert: " + height(result));

Pattern 2: Transaction-Protected Update

conn.AutoCommit = 'off';
try
    execute(conn, sqlStatement);
    commit(conn);
catch e
    rollback(conn);
    conn.AutoCommit = 'on'; %#ok<NASGU> restore before rethrowing
    rethrow(e);
end
conn.AutoCommit = 'on';

Pattern 3: DDL-then-Insert

execute(conn, "CREATE TABLE IF NOT EXISTS results (ID INT, Value DOUBLE)");
sqlwrite(conn, "results", data);

Checklist

Before finalizing, verify:

• [ ] Database connection established and verified (isopen(conn))
• [ ] No hardcoded credentials — uses getSecret or placeholders
• [ ] sqlwrite used for table inserts (not raw SQL INSERT for MATLAB data)
• [ ] Transactions used for multi-statement atomic operations
• [ ] AutoCommit restored to 'on' after transaction blocks
• [ ] Prepared statements closed with close(pstmt)
• [ ] Connection closed with close(conn) at the end

Troubleshooting

Issue: sqlwrite fails with "table already exists"

• Solution: sqlwrite creates the table if it doesn't exist but errors if the table exists with a different schema. Use sqlwrite to append to an existing table — column names and types must match.

Issue: sqlupdate not recognized

• Solution: sqlupdate requires R2023a or later. For older releases, use update or execute a raw SQL UPDATE statement with execute.

Issue: sqlupdate silently updates wrong number of rows

• Solution: The data table passed to sqlupdate must have either exactly 1 row (broadcasts to all matching rows) or exactly as many rows as the filter matches. ALWAYS verify the filter match count first with sqlread + the same RowFilter.

Issue: Transaction changes not visible after commit

• Solution: Verify AutoCommit was set to 'off' before the transaction. If AutoCommit is 'on', each statement auto-commits immediately.

Issue: Prepared statement errors with "parameter index out of range"

• Solution: Verify the parameter indices in bindParamValues match the number of ? placeholders in the SQL statement. Indices are 1-based.

Issue: Bulk insert runs out of memory

• Solution: sqlwrite has no BatchSize parameter. Chunk the MATLAB table manually in a loop — split data into slices of 5,000–50,000 rows and call sqlwrite on each slice.

Issue: runstoredprocedure fails with "wrong number of arguments"

• Solution: Verify the input argument count matches the stored procedure definition. For JDBC connections, output types must use java.sql.Types constants.

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