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What does this query mean: SELECT user_name, user_isp FROM users LEFT JOIN isps USING (user_id)
MySQL and SQL
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What does this query mean: SELECT user_name, user_isp FROM users LEFT JOIN isps USING (user_id)
It’s equivalent to saying SELECT user_name, user_isp FROM users LEFT JOIN isps WHERE users.user_id=isps.user_id
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Other Interview Questions
- What's MySQL
- What is DDL, DML and DCL?
- How do you get the number of rows affected by query?
- If the value in the column is repeatable, how do you find out the unique values?
- How do you return the a hundred books starting from 25th?
- You wrote a search engine that should retrieve 10 results at a time, but at the same time you’d like to know how many rows there’re total. How do you display that to the user?
- How would you write a query to select all teams that won either 2, 4, 6 or 8 games?
- How would you select all the users, whose phone number is null?
- What does this query mean: SELECT user_name, user_isp FROM users LEFT JOIN isps USING (user_id)
- How do you find out which auto increment was assigned on the last insert?
- What does –i-am-a-dummy flag to do when starting MySQL?
- On executing the DELETE statement I keep getting the error about foreign key constraint failing. What do I do?
- When would you use ORDER BY in DELETE statement?
- How can you see all indexes defined for a table?
- How would you change a column from VARCHAR(10) to VARCHAR(50)?
- How would you delete a column?
- How would you change a table to InnoDB?
- When you create a table, and then run SHOW CREATE TABLE on it, you occasionally get different results than what you typed in. What does MySQL modify in your newly created tables?
- How do I find out all databases starting with ‘tech’ to which I have access to?
- How do you concatenate strings in MySQL?
- How do you get a portion of a string?
- What’s the difference between CHAR_LENGTH and LENGTH?
- How do you convert a string to UTF-8?
- What do % and _ mean inside LIKE statement?
- What does + mean in REGEXP?
- How do you get the month from a timestamp?
- How do you offload the time/date handling to MySQL?
- How do you add three minutes to a date?
- What’s the difference between Unix timestamps and MySQL timestamps?
- How do you convert between Unix timestamps and MySQL timestamps?
- What are ENUMs used for in MySQL?
- How are ENUMs and SETs represented internally?
- How do you start and stop MySQL on Windows?
- How do you start MySQL on Linux?
- Explain the difference between mysql and mysqli interfaces in PHP?
- What’s the default port for MySQL Server?
- What does tee command do in MySQL?
- Can you save your connection settings to a conf file?
- How do you change a password for an existing user via mysqladmin?
- Use mysqldump to create a copy of the database?
- Have you ever used MySQL Administrator and MySQL Query Browser?
- What are some good ideas regarding user security in MySQL?
- Explain the difference between MyISAM Static and MyISAM Dynamic.
- What does myisamchk do?
- Explain advantages of InnoDB over MyISAM?
- Explain advantages of MyISAM over InnoDB?
- What are HEAP tables in MySQL?
- How do you control the max size of a HEAP table?
- What are CSV tables?
- Explain federated tables.
- What is SERIAL data type in MySQL?
- What happens when the column is set to AUTO INCREMENT and you reach the maximum value for that table?
- Explain the difference between BOOL, TINYINT and BIT.
- Explain the difference between FLOAT, DOUBLE and REAL.
- If you specify the data type as DECIMAL (5,2), what’s the range of values that can go in this table?
- What happens if a table has one column defined as TIMESTAMP?
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- The Main Features of MySQL
- Database Basics
- MySQL Command Interpreter
- Installing a MySQL Binary Distribution
- MySQL - Quick Installation Overview
- MySQL - MySQL Extensions to ANSI SQL92
- MySQL - Running MySQL in ANSI Mode
- Functionality Missing from MySQL - Sub-selects
- Functionality Missing from MySQL - SELECT INTO TABLE
- Functionality Missing from MySQL - Transactions
- Functionality Missing from MySQL - Stored Procedures and Triggers
- Functionality Missing from MySQL - Foreign Keys
- MySQL - Reasons NOT to Use Foreign Keys constraints
- Functionality Missing from MySQL - `--' as the Start of a Comment
- Functionality Missing from MySQL - How to Cope Without COMMIT/ROLLBACK
- MySQL - General Security
- How to Make MySQL Secure Against Crackers
- MySQL - Startup options to mysqld which concerns security
- MySQL - What the Privilege System Does
- MySQL - User Names and Passwords
- How to connecting to the MySQL Server
- MySQL - Keeping Your Password Secure
- Privileges Provided by MySQL
- MySQL - How the Privilege System Works
- MySQL - Access Control, Stage 1: Connection Verification
- MySQL - Access Control
- MySQL - When Privilege Changes Take Effect
- Setting Up the Initial MySQL Privileges
- Adding New User Privileges to MySQL
- MySQL - Setting Up Passwords
- MySQL - Causes of Access denied Errors
- Replication in MySQL
- MySQL - Replication Implementation Overview
- MySQL - how to set up complete replication on your current MySQL server
- MySQL - Replication Features and known problems
- MySQL - SQL Commands Related to Replication
- MySQL - Why do I sometimes see more than one Binlog_Dump thread on the master after I have restarted the slave?
- MySQL - How do I rotate replication logs?
- MySQL - How do I upgrade on a hot replication setup?
- MySQL - What issues should I be aware of when setting up two-way replication?
- MySQL - How can I use replication to improve performance of my system?
- MySQL - What should I do to prepare my client code to use performance-enhancing replication?
- MySQL - When and how much can MySQL replication improve the performance of my system?
- MySQL - How can I use replication to provide redundancy/high availability?
- MySQL - Troubleshooting Replication
- How to get Maximum Performance from MySQL
- MySQL - Optimization Overview
- MySQL - System/Compile Time and Startup Parameter Tuning
- MySQL - Disk Issues
- MySQL - Using Symbolic Links for Databases and Tables
- MySQL - Tuning Server Parameters
- How MySQL Opens and Closes Tables
- MySQL - Drawbacks to Creating Large Numbers of Tables in the Same Database
- MySQL - Why So Many Open tables?
- How MySQL Uses Memory
- How MySQL Locks Tables
- MySQL - Table Locking Issues
- How MySQL uses DNS
- MySQL - Get Your Data as Small as Possible
- How MySQL Uses Indexes
- MySQL - Speed of Queries that Access or Update Data
- MySQL - Estimating Query Performance
- MySQL - Speed of SELECT Queries
- How MySQL Optimizes WHERE Clauses
- How MySQL Optimizes DISTINCT
- How MySQL Optimizes LEFT JOIN and RIGHT JOIN
- How MySQL Optimizes LIMIT
- MySQL - Speed of INSERT Queries
- MySQL - Speed of UPDATE Queries
- MySQL - Speed of DELETE Queries
- MySQL - Other Optimization Tips
- MySQL - Using Your Own Benchmarks
- How MySQL Stores Its Row Data and Index Data?
- MySQL is Portability
- What Have We Used MySQL For?
- What is the difference between mysql_fetch_array and mysql_fetch_object?
- What are the different table present in MYsql?
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