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In PHP 7.4, MySQL 5.7, insert a field of type json, successfully insert the analysis of the value string(4) “null” (related to json_encode(null))

从日志中查看生成的 SQL，确认在更改表中记录中，赋值为 'null'

作者：

永夜

在

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1. In the MySQL table, the field type is JSON, and it is allowed to be null. as shown in Figure 1

在 MySQL 表，字段类型为 json，允许为 NULL
Figure 1

CREATE TABLE `table` (
  `schema` json DEFAULT NULL COMMENT '主题的Schema，包括页面、主题级别、组件级别',
);

2. Since only is_null() is judged in the program, if it is not null, the default is json format. When its value is String(4) “NULL”, the program throws a 500 exception. Displayed as null, indicating that its value is string(4) “null”, which is not as expected. Displayed as (NULL), indicating that its value is NULL, in line with expectations. as shown in Figure 2

由于在程序中仅判断了 is_null()，如果不为 NULL，则默认为 json 格式。当其值为 string(4) "null" 时，程序抛出 500 异常。显示为 null，表示其值为 string(4) "null"，不符合预期。显示为 (Null)，表示其值为 NULL，符合预期
Figure 2

3. View the generated sql from the log and confirm that in the record in the change table, the value is assigned tonull. as shown in Figure 3

从日志中查看生成的 SQL，确认在更改表中记录中，赋值为 'null'
Figure 3

update
  `table`
set
  `schema` = 'null',
  `checksum` = '0821db9eefeab3d74bbbac6f58cd68e4c8f1b9e2',
  `table`.`updated_at` = '2023-04-21 03:41:48'
where
  `id` = 432070

4. Print the changes of the relevant variables at the SQL generation. The results are as follows. as shown in Figure 4

打印生成 SQL 处的相关变量的变化情况。结果如下
Figure 4

$schema1 = $themeAsset->schema;
$schema2 = $this->themeSettingMigration->migrateJsonTemplate($filename, $schema, $themeInstallationTask, $availableVersions);
$themeAsset->schema = json_encode($schema2);
Log::info(
	$themeAsset->id,
	[
		'schema1' => $schema1,
		'schema2' => $schema2,
		'schema3' => $themeAsset->schema,
	]
);




[2023-04-21 11:41:48] local.INFO: 432062 {
    "schema1": null,
    "schema2": null,
    "schema3": "null"
}

5. This concludes that when json_encode(null) is returnednull, and eventually the SQL will be updated to the valuenull. Decide to adjust as follows, add judgment, when not null, only execute json_encode, otherwise return null


$schema = $this->themeSettingMigration->migrateJsonSettingsData($configSettingsDataSchema, $themeInstallationTask, $availableVersions);
$configSettingsData->schema = $schema ? json_encode($schema) : null;

 

 

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