FAQs(286 to 300)

286) What is a DB2 bind?

A) DB2 bind is a process that builds an access path to DB2 tables.

287) What is a DB2 access path?

A) An access path is the method used to access data specified in DB2 SQL statements.

288) What is a DB2 plan?

A) An application plan or package is generated by the bind to define an access path.

289) What is normalization and what are the five normal forms?

A) Normalization is a design procedure for representing data in tabular format. The five normal forms are progressive rules to represent the data with minimal redundancy.

290) What are foreign keys?

A) These are attributes of one table that have matching values in a primary key in another table, allowing for relationships between tables.

291) Describe the elements of the SELECT query syntax?

A) SELECT element FROM table WHERE conditional statement.

292) Explain the use of the WHERE clause?

A) WHERE is used with a relational statement to isolate the object element or row.

293) What techniques are used to retrieve data from more than one table in a single SQL statement?

A) Joins, unions and nested selects are used to retrieve data.

294) What do the initials DDL and DML stand for and what is their meaning?

A) DDL is data definition language and DML is data manipulation language. DDL statements are CREATE, ALTER, TRUNCATE. DML statements are SELECT, INSERT, DELETE and UPDATE.

295) What is a view? Why use it?

A) A view is a virtual table made up of data from base tables and other views, but not stored separately.

296) Explain an outer join?

A) An outer join includes rows from tables when there are no matching values in the tables.

297) What is a subselect? Is it different from a nested select?

A) A subselect is a select which works in conjunction with another select. A nested select is a kind of subselect where the inner select passes to the where criteria for the outer select.

298) What is the difference between group by and order by?

A) Group by controls the presentation of the rows, order by controls the presentation of the columns for the results of the SELECT statement.

299) Explain the EXPLAIN statement?

A) The explain statement provides information about the optimizer's choice of access path of the sql.

300) What is tablespace?

A) Tables are stored in tablespaces (hence the name)! There are three types of tablespaces: simple, segmented and partitioned.