alter composite primary key in cassandra CQL 3.0
There is no way to change a primary key, as it defines how your data is physically stored. You can create a new table with the new primary key, copy data from the old one, and then drop the old table.
composite-primary-key
JPA COUNT with composite primary key query not working
Use count(d.ertek) or count(d.id) instead of count(d). This can be happen when you have composite primary key at your entity.
Hibernate: Where do insertable = false, updatable = false belong in composite primary key constellations involving foreign keys?
Let me answer step by step. 1. When do you need ` insertable = false, updatable = false`? Let’s look at the below mapping, public class Zip { @ManyToOne @JoinColumn(name = “country_code”, referencedColumnName = “iso_code”) private Country country = null @Column(name = “country_code”) private String countryCode; } Here we are referring to the same column … Read more
WHERE col1,col2 IN (…) [SQL subquery using composite primary key]
sqlite> create table foo (a,b,c); sqlite> create table bar (x,y); sqlite> select * from foo where exists (select 1 from bar where foo.a = bar.x and foo.b = bar.y); Replace the select 1 from bar with your select … many tuples of a/b values …. Or create a temporary table of your select … many … Read more
Define a unique primary key based on 2 columns
add_index :words, [“id”, “language_id”], :unique => true It should work. Maybe you have already some non-unique data in your db and index can’t be created? But (as @Doon noticed it will be redundant since id is always unique). So you need create primary key on two columns. To define 2 column primary key in rails … Read more
Primary key for multiple columns in PostgreSQL?
There can only be one primary key per table – as indicated by the word “primary”. You can have additional UNIQUE columns like: CREATE TABLE test( sl_no int PRIMARY KEY, — NOT NULL due to PK emp_id int UNIQUE NOT NULL, emp_name text, emp_addr text ); Columns that are (part of) the PRIMARY KEY are … Read more
MongoDB and composite primary keys
You should go with option 1. The main reason is that you say you are worried about performance – using the _id index which is always there and already unique will allow you to save having to maintain a second unique index. For option 1, I’m worried about the insert performance do to having non … Read more
How can I alter a primary key constraint using SQL syntax?
Yes. The only way would be to drop the constraint with an Alter table then recreate it. ALTER TABLE <Table_Name> DROP CONSTRAINT <constraint_name> ALTER TABLE <Table_Name> ADD CONSTRAINT <constraint_name> PRIMARY KEY (<Column1>,<Column2>)
SQL join with composite primary key
You can use AND in the expression for the ON criteria and demand the fields are all equal there. SELECT * FROM Table1 INNER JOIN Table2 ON Table1.Key1 = Table2.Key1 AND Table1.Key2 = Table2.Key2 AND Table1.Key3 = Table2.Key3
How to define composite primary key in SQLAlchemy
I agree that the question is vague. But you can use the following as a guideline. This will select from a trial1 table in a test database in MySQL. Commented out parts are there as an alternative way to setup primary key constraints. from sqlalchemy import String, create_engine, MetaData, Column from sqlalchemy.ext.declarative import declarative_base # … Read more