EC
1263
MySQLWARNINGNotableData ImportHIGH confidence

Column set to default: NULL supplied to NOT NULL column

Production Risk

Medium — rows are imported with unexpected default values; data may be incorrect.

What this means

ER_WARN_NULL_TO_NOTNULL (1263, SQLSTATE 22004) is a warning issued when a NULL value is assigned to a NOT NULL column during LOAD DATA INFILE. MySQL sets the column to its default value instead.

Why it happens
  1. 1Input file contains empty or NULL values for a NOT NULL column
  2. 2Strict mode is not enabled, so MySQL substitutes the default instead of rejecting the row
How to reproduce
trigger — this will error
trigger — this will error
LOAD DATA INFILE '/data/import.csv'
INTO TABLE orders
FIELDS TERMINATED BY ','
(id, customer_id, amount);
-- If amount field is empty in row 7:
-- Warning 1263: Column 'amount' set to default value; NULL supplied to NOT NULL column at row 7

expected output

Warning (Code 1263): Column 'amount' set to default value; NULL supplied to NOT NULL column at row 7

Fix

Clean the input data to remove NULL values

Clean the input data to remove NULL values
-- Preprocess the CSV to replace empty fields with 0 or appropriate defaults
-- Or enable strict mode to reject rows with NULL in NOT NULL columns:
SET SESSION sql_mode = 'STRICT_TRANS_TABLES';

Why this works

In strict mode, NULL in a NOT NULL column raises an error instead of silently using the default.

Sources
Official documentation ↗

MySQL 8.0 — 1263 ER_WARN_NULL_TO_NOTNULL

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