primary-key

问题 I have a table "MY_TABLE" in Snowflake that I would like to add an identity column to. I tried ALTER TABLE "MY_TABLE" ADD COLUMN primary_key int IDENTITY(1,1); But this returns SQL compilation error: Cannot add column 'PRIMARY_KEY' with non-constant default to non-empty table 'MY_TABLE'. Is this just not possible in snowflake? To try to get around this limitation, I tried to create a temp version of the table CREATE OR REPLACE TABLE "MY_TABLE_TEMP" LIKE "MY_TABLE" ALTER TABLE "MY_TABLE_TEMP"

问题 The question is that, When we use INSERT INTO USERS (login, email, name, login_count) values ('jbellis', 'jbellis@datastax.com', 'Jonathan Ellis', 1) IF NOT EXISTS in IF NOT EXIST exactly which columns are compared together? primary key(partition-key + clustering-key)? or just partition-key? 回答1: Here is a diagram of the 4 phases of LWT: http://www.slideshare.net/doanduyhai/cassandra-introduction-nantesjug/89 The original blog post is here: http://www.datastax.com/dev/blog/lightweight

问题 I'm using Django 2.0, Python 3.7, and MySql 5. I have the following two models, the second dependent on the first ... class CoopType(models.Model): name = models.CharField(max_length=200, null=False) class Meta: unique_together = ("name",) class Coop(models.Model): name = models.CharField(max_length=250, null=False) type = models.ForeignKey(CoopType, on_delete=None) address = AddressField(on_delete=models.CASCADE) enabled = models.BooleanField(default=True, null=False) phone =

问题 I'm using Django 2.0, Python 3.7, and MySql 5. I have the following two models, the second dependent on the first ... class CoopType(models.Model): name = models.CharField(max_length=200, null=False) class Meta: unique_together = ("name",) class Coop(models.Model): name = models.CharField(max_length=250, null=False) type = models.ForeignKey(CoopType, on_delete=None) address = AddressField(on_delete=models.CASCADE) enabled = models.BooleanField(default=True, null=False) phone =

问题 Closed . This question needs details or clarity. It is not currently accepting answers. Want to improve this question? Add details and clarify the problem by editing this post. Closed 3 months ago . Improve this question I have created table name as d with ID column as primary key and then just inserted records as shown in output, but after fetching all records this output still displayed same as order in which records are inserted. but output as a see now not in ordered form. 回答1: PostgreSQL

问题 Closed . This question needs details or clarity. It is not currently accepting answers. Want to improve this question? Add details and clarify the problem by editing this post. Closed 3 months ago . Improve this question I have created table name as d with ID column as primary key and then just inserted records as shown in output, but after fetching all records this output still displayed same as order in which records are inserted. but output as a see now not in ordered form. 回答1: PostgreSQL

问题 Closed . This question needs details or clarity. It is not currently accepting answers. Want to improve this question? Add details and clarify the problem by editing this post. Closed 3 months ago . Improve this question I have created table name as d with ID column as primary key and then just inserted records as shown in output, but after fetching all records this output still displayed same as order in which records are inserted. but output as a see now not in ordered form. 回答1: PostgreSQL

问题 I'm working on a distributed system that uses CQRS and DDD principles. Based on that I decided that the primary keys of my entities should be guids, which are generated by my domain (and not by the database). I have been reading about guids as primary keys. However, it seems that some of the best practices are not valid anymore if applied to Azure SQL database. Sequential guids are nice if you use an on premise SQL server machine - the sequential guids that are generated will always be unique

问题 We are using UUID as primary key for out oracle DB, and trying to determine an appropriate max character length for the VARCHAR. Apparently this is 36 characters but we have noticed UUID'S generated which are longer than this - up to 60 characters in length. Does anyone know a suitable max char length for UUID?? 回答1: Section 3 of RFC4122 provides the formal definition of UUID string representations. It's 36 characters (32 hex digits + 4 dashes). Sounds like you need to figure out where the

来源： https://stackoverflow.com/questions/3379292/is-an-index-needed-for-a-primary-key-in-sqlite