Why Am I Getting a MySQL 'Can't Create Table' Error (Errorno: 150)?

Troubleshooting MySQL's "Can't Create Table" Error (Errorno: 150)

Creating a table via SQL script can sometimes result in the error "MySQL: Can't create table (errno: 150)." This frequently occurs during .sql file imports, leading to table creation failure.

Root Cause:

The error, "Error 150: Foreign key constraint is incorrect," indicates a mismatch between the table definition and a referencing foreign key constraint. The newly created table doesn't meet the foreign key's requirements.

Solution:

MySQL's FOREIGN KEY documentation states: A recreated table must precisely match the foreign key constraints referencing it. This means identical column names, data types, and indexes on the referenced keys are crucial. Failure to meet these conditions yields Error 1005, with Error 150 noted in the message, signaling an incorrectly formed foreign key constraint.

Therefore:

• Column names and data types must match the referenced constraint.
• Indexes on referenced keys are mandatory.
• The table definition must not violate the foreign key constraint.

Debugging Steps:

1. Column Definition Verification: Confirm the new table's column names and data types mirror those in the original schema.
2. Index Check: Verify the existence of indexes on referenced keys in both the original and new tables.
3. Foreign Key Constraint Review: Carefully examine the foreign key constraints referencing the table. Ensure they're accurately defined and point to the correct columns in the referenced table.
4. .sql Script Inspection: Thoroughly check the .sql file for completeness and the absence of syntax errors that might affect table definitions or constraints.

By rectifying these potential inconsistencies, the table definition will align with the referencing foreign key constraints, resolving the "Error 150: Foreign key constraint is incorrect" problem.

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