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SQL What is DBMS? - Database management system What is RDBMS? - Relational database management system - Stores data into tables(columns and rows) - SQL Server is an example of RDBMS What does SQL stand for? - Structured Query Language Who determines the standards for SQL? - ANSI (American national Standards Institute) What are the versions of SQL? - 86th to 2016 Users vs Schemas? - USERS = SCHEMAS There are 4 main categories of SQL statements - DDL(Data definition language) o CREATE, ALTER, DROP o In ALTER you can add/remove columns and constraints o Examples of constraints ♣ Primary key used to ID a row or record, null values are not allowed • Primary key = unique key + not null constraint ♣ Unique constraint null values are allowed ♣ Foreign key a column in a table that refers to the primary key of another table ♣ Check ♣ Default ♣ Index ♣ Not Null - DML (Data Manipulation Language) o SELECT, DELETE, INSERT, UPDATE o Objects created using DML: ♣ Table ♣ Index it is used retrieve data faster • Optimizes access to data in a shema ♣ View it is a stored query ♣ Sequence ♣ Synonym o SELECT: if you are using 2 or more tables: ♣ You need a parent/child or primary key/foreign key relationship ♣ You will also need to use joins when you are getting data from 1 or more tables ♣ Types of joins” • Inner join o Returns records that have matching values in both tables • Left join o Return all records from the left table, and the matched records from the right table • Right join o Return all records from the right table, and the matched records from the left table • Full join o Return all records when there is a match in either left or right table - DCL (Data Control Language) o Control the level of access that users have o GRANT, REVOKE - TCL (Transaction Control Language) o COMMIT, ROLLBACK o Savepoint partial rollback What is the difference between truncate and drop? - Truncate will keep the table structure and delete the rows and you can’t rollback o Empties the table - Drop will drop the entire table What are set operators? - They combine two component queries into one result - Queries containing set operators are called Compound queries - Examples of set operators o Union - All distinct rows selected by either query o Union all - All rows selected by either query, including all duplicates o Intersect - All distinct rows selected by both queries o Minus - All distinct rows selected by the first query but not the second What is the UNION Operator? - It is used to combine the results of two SELECT statements - They must have the same number of columns and data types AND be in the same order What is the difference between ORDER BY and GROUP BY? - Order by is only for sorting purposes - Group by used with aggregate functions (COUNT, MAX, MIN, SUM, AVG) to group the result-set by one or more columns What is the difference between the WHERE and HAVING clause?   - Where is used to filter records from a result - HAVING is used to filer values from a group o Used with group by What is the purpose of JOIN in SQL?   - Combines one or more tables in a relational database How do you select all rows and columns of a table in SQL?   - SELECT * FROM… When using NULL.. - ___ IS Null (Correct) - ___ = NULL (incorrect) o because null is not equal to null or null is not not equal to null What is a subquery? - Query with in a larger query What are examples of oracle datatypes? - Char - Number - Float - Integer - Varchar2 What is normalization? - It is a process to remove redundancy across tables - Instead of having multiple of the same fields in different tables you can consolidate them into and ID so you are able to refer to one ID . Difference between INNER JOIN and OUTER JOIN? - What is a foreign/primary key?   - A primary key uniquely identifies each row in a database o Can’t contain null values!!! - A foreign key is used to link data between two tables together Give a simple CRUD query -
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Entry Level Software Engineer

Interviewed at Revature

3.7★
Nov 3, 2017

SQL What is DBMS? - Database management system What is RDBMS? - Relational database management system - Stores data into tables(columns and rows) - SQL Server is an example of RDBMS What does SQL stand for? - Structured Query Language Who determines the standards for SQL? - ANSI (American national Standards Institute) What are the versions of SQL? - 86th to 2016 Users vs Schemas? - USERS = SCHEMAS There are 4 main categories of SQL statements - DDL(Data definition language) o CREATE, ALTER, DROP o In ALTER you can add/remove columns and constraints o Examples of constraints ♣ Primary key used to ID a row or record, null values are not allowed • Primary key = unique key + not null constraint ♣ Unique constraint null values are allowed ♣ Foreign key a column in a table that refers to the primary key of another table ♣ Check ♣ Default ♣ Index ♣ Not Null - DML (Data Manipulation Language) o SELECT, DELETE, INSERT, UPDATE o Objects created using DML: ♣ Table ♣ Index it is used retrieve data faster • Optimizes access to data in a shema ♣ View it is a stored query ♣ Sequence ♣ Synonym o SELECT: if you are using 2 or more tables: ♣ You need a parent/child or primary key/foreign key relationship ♣ You will also need to use joins when you are getting data from 1 or more tables ♣ Types of joins” • Inner join o Returns records that have matching values in both tables • Left join o Return all records from the left table, and the matched records from the right table • Right join o Return all records from the right table, and the matched records from the left table • Full join o Return all records when there is a match in either left or right table - DCL (Data Control Language) o Control the level of access that users have o GRANT, REVOKE - TCL (Transaction Control Language) o COMMIT, ROLLBACK o Savepoint partial rollback What is the difference between truncate and drop? - Truncate will keep the table structure and delete the rows and you can’t rollback o Empties the table - Drop will drop the entire table What are set operators? - They combine two component queries into one result - Queries containing set operators are called Compound queries - Examples of set operators o Union - All distinct rows selected by either query o Union all - All rows selected by either query, including all duplicates o Intersect - All distinct rows selected by both queries o Minus - All distinct rows selected by the first query but not the second What is the UNION Operator? - It is used to combine the results of two SELECT statements - They must have the same number of columns and data types AND be in the same order What is the difference between ORDER BY and GROUP BY? - Order by is only for sorting purposes - Group by used with aggregate functions (COUNT, MAX, MIN, SUM, AVG) to group the result-set by one or more columns What is the difference between the WHERE and HAVING clause?   - Where is used to filter records from a result - HAVING is used to filer values from a group o Used with group by What is the purpose of JOIN in SQL?   - Combines one or more tables in a relational database How do you select all rows and columns of a table in SQL?   - SELECT * FROM… When using NULL.. - ___ IS Null (Correct) - ___ = NULL (incorrect) o because null is not equal to null or null is not not equal to null What is a subquery? - Query with in a larger query What are examples of oracle datatypes? - Char - Number - Float - Integer - Varchar2 What is normalization? - It is a process to remove redundancy across tables - Instead of having multiple of the same fields in different tables you can consolidate them into and ID so you are able to refer to one ID . Difference between INNER JOIN and OUTER JOIN? - What is a foreign/primary key?   - A primary key uniquely identifies each row in a database o Can’t contain null values!!! - A foreign key is used to link data between two tables together Give a simple CRUD query -

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