When the database is set to AUTOCLOSE = ON, an operation that initiates an automatic database shutdown clears the plan cache for the instance of SQL Server. Clearing the plan cache causes a recompilation of all
There is an IMO big caveat of bulk_create(): It does not set primary key of objects it creates. In my current project, using bulk_create would improve performance, but as I often need an id of the newly created objects, I have to save them one by one. ...
When the database is set to AUTOCLOSE = ON, an operation that initiates an automatic database shutdown clears the plan cache for the instance of SQL Server. Clearing the plan cache causes a recompilation of all subsequent execution plans and can cause a sudden, temporary decrease in query pe...
| <HADR_options> | <mixed_page_allocation_option> | <optimized_locking> | <parameterization_option> | <query_store_options> | <recovery_option> | <remote_data_archive_option> | <persistent_log_buffer_option> | <service_broker_option> | <snapshot_option> | <sql_option> | <suspend_for...
possible_keys: PRIMARY key: PRIMARY key_len: 4 ref: NULL rows: 4 Extra: Using where; Using index 1 row in set (0.00 sec) mysql> 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 表明存储引擎从索引的起始处开始,获取所有的行,直到actor_id<4为假,服务器无法告诉...
CREATETABLEcategories(idINTPRIMARYKEYAUTO_INCREMENT,nameVARCHAR(50),parent_idINT); 1. 2. 3. 4. 5. 在这个表中,id表示分类的唯一标识,name表示分类的名称,parent_id表示该分类的父分类ID。 示例数据 INSERTINTOcategories(name,parent_id)VALUES('Electronics',NULL),('Laptops',1),('Desktops',1),('...
还要注意的是,即使对一个未执行的 QuerySet 进行切片,返回另一个未执行的 QuerySet,也不允许进一步修改它(例如,添加更多的过滤器,或修改排序),因为这不能很好地翻译成 SQL,也没有明确的含义。 Pickle 序列化/缓存。 关于pickling QuerySets 时涉及的细节,请参见下一节。就本节而言,重要的是,结果是从数据库...
SQL CREATETABLEdbo.t ( aINTPRIMARYKEY, b1INT); GOCREATEVIEWdbo.vASSELECTb1ASb2FROMdbo.t; GO EXEC sp_describe_first_result_set N'SELECTb2ASb3FROMdbo.v', NULL, 0; 以下为部分结果集。 is_hiddencolumn_ordinalnamesource_schemasource_tablesource_columnis_part_of_unique_key ...
MySQL localhost:3381sslSQL>\sqlMySQL localhost:3381sslSQL>createdatabaseytt;Query OK,1rowaffected(0.0167sec)MySQL localhost:3381sslSQL>useytt;Defaultschemasetto`ytt`.Fetchingtableandcolumnnamesfrom`ytt`forauto-completion...Press^Ctostop.MySQL localhost:3381ssl yttSQL>createtablet1(idintprimarykey,r1...
class Book(models.Model): id = models.AutoField(primary_key=True) title = models.CharField(max_length=32) price = models.DecimalField(max_digits=8,decimal_places=2,) pub_date = models.DateTimeField() #必须存这种格式"2012-12-12" publish = models.CharField(max_length=32) def __str__(...