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What key defines a relationship between two tables 1 Primary key 2 Secondary key 3 Foreign key?
Foreign key is used to define a relationship between two tables by referencing the primary key of another table. It ensures data integrity and enforces referential integrity between the related tables.
What is difference between natural join equijoin and outer join?
Equijoin - Joins two or more tables where the specified columns are equal. Returns only those records found in both tables. Outer join - Joins two or more tables on the specified columns, returning all the values from table 1 regardless of whether they are in table 2. Natural Join - Joins two tables on all like column names.
Difference between cartesian product and full outer join?
Full outer join will fetch at maximum 'addition of 2 tables' Ex: Table A - 2 rows; Table B - 3 rows. Full outer join will fetch in 2+3 = 5 rows. Where as in Cartesian product will fetch in 'product of 2 tables'. Ex: Table A - 2 rows; Table B - 3 rows. Full outer join will fetch in 2x3 = 6 rows
Within the context of SQL what is a Complex Join?
I've seen discussions involving slightly different definitions, so here are two. 1. A complex join involves the joining of more than 2 tables and a filter - also known as a mutable join with a filter. 2. A join that has a conditional statement such as <, >, Not, >=, <=, etc. instead of =.
Explain two rules in relational model of database systems?
1) Entity Integrity: In a base relation, no attribute of a primary key can be null. 2) Referential Integrity: If foreign key exists in a relation, either foreign key value must match a candidate key value of some tuple in its home relation or foreign key value must be wholly null
How old do you have to be to join the military in France?
The official age requirement to join the French Foreign Legion is 17 1/2 (with parental consent) - 40.
Join query in sql server 2005?
Join query are basically of three types : 1) Cross Join -- That is use to retrieve data from two tables on a condition (optional), there we get m*n no. of records(m is no of rec in first table and n is the no. of records in another table) 2) Inner Join : we use this join to retrieve values from two tables that satisfies given matching condition : as :: select Product_Category from Product_Detail INNER JOIN Product_Scenerio ON Product_Detail.Product_Id = Product_Detail.Product_Id. Product_Scenerio . 3) Outer Join : this is used in three way: a) Left Outer Join -- it is used to retrieve records from both tables that satisfies given condition including all records from left(First) table whether it do not satisfy condition ...try it practically ** related columns in right table has NULL values in records b) Right Outer Join :: It is used when we want to fetch all records from right(second) table whether that do not match with condition specified with JOIN . ** related columns in right table has NULL values in records c) Full Outer Join :: It is combination of Inner join + left Outer join + right Outer join .Here we get all records from both tables that do not match condition .
Different types of joins in DBMS with examples?
Inner Join-: It is also called simple join. It returns all rows from both tables if there is any match.SELECT * FROM R1, R2 WHERE R1.r1_field = R2.r2_field; SELECT * FROM R1 INNER JOIN R2 ON R1.field = R2.r2_fieldNatural Joins -: it is used when two tables have all columens with same nameLeft [Outer] Join -: Returns all rows from table 1 even if there is no match in table 2, all mismatch will be printed as nullRight [Outer] Join -: Returns all rows from table 2 even if there is no match in table 1, all mismatch will be printed as nullCross Join -:This type of join is rarely used as it does not have a join condition, so every row of table 1 is joined to every row of table 2. For example, if both tables contain 100 rows the result will be 10,000 rows. This is sometimes known as a cartesian product and can be specified in either one of the following ways:SELECT * FROM table 1 CROSS JOIN table2SELECT * FROM table1, table2kailash c kandpalhttp://www.valve-store.com
Why were the last 2 tables in ancient Rome created?
Frist 10 Tables 450 BC, last 2 tables 449 BC
How do you join two tables in an Access query where it returns all fields that are not in one of the tables only?
I am confused with your question, so I will do both interpretations. The query wizards may help you but you didn't say which Access you are using so we will do it in the query builder instead. ................. You have a table with 25 keys and a table with 10 foreign keys for this example. This could be a one-to-one relationship or a one-to-many in which the 'many' table just has records that match some of the keys in the 'one' table. You want to see all the 25-key table and anything in the 10-key table that matches. So 15 of the keys from 25-key will not match the 10-key table but you want to see them anyway. In the query builder, link the key fields going from the 25 table to the 10 table. Then right-click on the link and select the 2nd option "show all from 25-table and the matching records in the 10-table". Run the query. You will see everything from the 25-table. In the fields from the 10-table there will be blanks where nothing matches. .................. My second guess is you want to see the ones that don't have a matching key. If it matches you don't care about it, like when you are trying to find keys to fix so you can have integrity between the tables. You have a table with 10 keys and a table with 25 foreign keys and you need to find those extra 15 foreign keys so you can fix the data integrity. (Notice that this is the opposite of the 2 tables in example 1 - the extras are in the foreign key table. You will most often have this problem when you import data, not when you are doing data entry.) In the query builder link the tables, 25-table to 10-table. Again do the right-click on the link and select the 2nd option. Show only the fields of the 25-table down in the bottom part. Now drag the key field from the 10-table down to the grid. Un-check the box under the field name and table name. In the criteria row type "Is Null". Run the query. You will see the records from the 25-foriegn key table that need to have keys set up in the 10-key table. .................. In both cases, if you want to filter the records do it in queries and then link the filter queries instead of the tables. This is an over-simplification and I am assuming you have actual key fields set up, like an autonumber field on the 'one' side. If you have something like "blue", "red", "green" as your key field you have some real work to do.
Difference between FULL JOIN and INNER JOIN in sql?
An INNER JOIN between two tables means that the joining values have to be present in both tables, while an FULL JOIN means that the values can be in either of the two tables. This is also know as a FULL OUTER JOIN.As an example, imagine a customer table with a code,name and type and an auxiliary table with a type id and type description;select * from Customer1 Record One 0012 Number 2 0013 The third 002Select * from CustomerType001 Type_one003 Another One(you'll notice that the type code '002' is missing).select Customer.Name, Customer.TypeCode, TypeCode.Description from Customer INNER JOIN CustomerType on (CustomerType.Code = Customer.TypeCode)Record One 001Number 2 001(The third record is missing because there wasn't a corresponding value in the CustomerType table for the inner join)select Customer.Name, Customer.TypeCode, TypeCode.Description from Customer FULL JOIN CustomerType on (CustomerType.Code = Customer.TypeCode)Record One 001Number 2 001The third 002(Which works because of the FULL - aka OUTER - JOIN)
Is 121 counted in the 2 times tables?
121 is not in the 2 times tables because it is an odd number.
