General MySQL Oracle SQL Server

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What Are Group Functions in MySQL
What Are Group Functions in MySQL? Group functions are functions applied to a group of rows. Examples of group functions are: COUNT(*) - Returns the number of rows in the group. MIN(exp) - Returns the minimum value of the expression evaluated on each row of the group. MAX(exp) - Returns the maximum ... 2018-01-06, 2228🔥, 0💬

Filerting out Duplications in Returning Rows in MySQL
How To Filter Out Duplications in Returning Rows in MySQL? If there are duplications in the returning rows, and you want to remove the duplications, you can use the keyword DISTINCT in the SELECT clause. The DISTINCT applies to the combination of all data fields specified in the SELECT clause. The t... 2018-01-06, 2192🔥, 0💬

Using Table Alias Names in MySQL
How To Define and Use Table Alias Names in MySQL? When column names need to be prefixed with table names, you can define table alias name and use them to prefix column names as shown in the following select statement: mysql&gt; SELECT l.id, l.url, r.comment FROM fyi_links l INNER JOIN fyi_rates ... 2017-12-31, 2415🔥, 0💬

SELECT Statements with JOIN and Subqueries in MySQL
Where to find answers to frequently asked questions on SELECT Statements with JOIN and Subqueries in MySQL? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on SELECT Statements with JOIN and Subqueries in MySQL. Clear answers are provided with tutori... 2017-12-31, 2339🔥, 0💬

Query with an Inner Join in MySQL
How To Write a Query with an Inner Join in MySQL? If you want to query from two tables with an inner join, you can use the INNER JOIN ... ON clause in the FROM clause. The tutorial exercise below creates another testing table and returns output with an inner join from two tables: fyi_links and fyi.r... 2017-12-31, 2282🔥, 0💬

Types of Table Joins in MySQL
How To Join Two Tables in a Single Query in MySQL? Two tables can be joined together in a query in 4 ways: Inner Join: Returns only rows from both tables that satisfy the join condition. Left Outer Join: Returns rows from both tables that satisfy the join condition, and the rest of rows from the fir... 2017-12-31, 2256🔥, 0💬

Using Group Functions in the ORDER BY Clause in MySQL
Can Group Functions Be Used in the ORDER BY Clause in MySQL? If the query output is aggregated as groups, you can sort the groups by using group functions in the ORDER BY clause. The following statement returns how many links were created in each year in each tag. The group output is sorted by the c... 2017-12-31, 2133🔥, 0💬

Date and Time Intervals in MySQL
What Are Date and Time Intervals in MySQL? A date and time interval is special value to be used to increment or decrement a date or a time at a given date or time unit. A data and time interval should be expression in the format of "INTERVAL expression unit", where "unit" and "expression" should fol... 2017-12-26, 2476🔥, 0💬

Entering Microseconds in SQL Statements in MySQL
How To Enter Microseconds in SQL Statements in MySQL? If you want to enter microseconds in a SQL statements, you can enter them right after the time string as a 6-digit number delimited with '.'. '0' will be padded to right if not enough digits. Here are some good examples: SELECT TIME('1997/01/31 0... 2017-12-26, 2292🔥, 0💬

Writing Date and Time Literals in MySQL
How To Write Date and Time Literals in MySQL? MySQL offers a number of formats for you to use to enter date and time literals: ANSI standard format: "YYYY-MM-DD HH:MM:SS". Non-standard limiters. Like: "YYYY/MM/DD HH^MM^SS" or "YYYY.MM.DD HH-MM-SS". No limiters. Like: "YYYYMMDD" for a date or "HHMMSS... 2017-12-26, 2290🔥, 0💬

Converting Dates to Character Strings in MySQL
How To Convert Dates to Character Strings in MySQL? You can convert dates to character strings using the DATE_FORMAT(date, format) function. MySQL supports the following basic formatting codes: %a Abbreviated weekday name (Sun..Sat) %b Abbreviated month name (Jan..Dec) %c Month, numeric (0..12) %D D... 2017-12-26, 2276🔥, 0💬

Converting Character Strings to Dates in MySQL
How To Convert Character Strings to Dates in MySQL? If you have a character string that represents a date, and you want to convert it into a date value, you can use the STR_TO_DATE(string, format) function. STR_TO_DATE() shares the same formatting codes with DATE_FORMAT() function. The tutorial exer... 2017-12-26, 2257🔥, 0💬

Presenting a Past Time in Hours, Minutes and Seconds in MySQL
How To Present a Past Time in Hours, Minutes and Seconds in MySQL? If you want show an article was posted "n hours n minutes and n seconds ago", you can use the TIMEDIFF(NOW(), pastTime) function as shown in the following tutorial exercise: SELECT TIMEDIFF(NOW(), '2006-07-01 04:09:49') FROM DUAL; 06... 2017-12-26, 4248🔥, 0💬

Calculating the Difference between Two Time Values in MySQL
How To Calculate the Difference between Two Time Values in MySQL? If you have two time values, and you want to know the time difference between them, you can use the TIMEDIFF(time1, time2) function as shown below: SELECT TIMEDIFF(TIME('19:26:50'), TIME('09:26:50')) FROM DUAL; 10:00:00 SELECT TIMEDIF... 2017-12-26, 3538🔥, 0💬

Decrementing a Date by 1 in MySQL
How To Decrement Dates by 1 in MySQL? If you have a date, and you want to decrement it by 1 day, you can use the DATE_SUB(date, INTERVAL 1 DAY) function. You can also use the date interval subtraction operation as "date - INTERVAL 1 DAY". The tutorial exercise below gives you some good examples: SEL... 2017-12-26, 2982🔥, 0💬

Calculating the Difference between Two Dates in MySQL
How To Calculate the Difference between Two Dates in MySQL? If you have two dates, and you want to know how many days between them, you can use the DATEDIFF(date1, date2) function as shown below: SELECT DATEDIFF(DATE('1997-02-28'), DATE('1997-03-01')) FROM DUAL; -1   ⇒ Calculating the Difference bet... 2017-12-26, 2818🔥, 0💬

Incrementing a Date by 1 in MySQL
How To Increment Dates by 1 in MySQL? If you have a date, and you want to increment it by 1 day, you can use the DATE_ADD(date, INTERVAL 1 DAY) function. You can also use the date interval add operation as "date + INTERVAL 1 DAY". The tutorial exercise below gives you some good examples: SELECT DATE... 2017-12-26, 2562🔥, 0💬

Returning Top 5 Rows in MySQL
How To Return Top 5 Rows in MySQL? If you want the query to return only the first 5 rows, you can use the LIMIT clause, which takes one parameter as the maximum number of rows to return. The following statement returns the first 5 rows from the fyi_links: mysql&gt; SELECT id, url, counts, tag FR... 2017-12-21, 2387🔥, 0💬

Merge Outputs from Two Queries in MySQL
How To Use UNION to Merge Outputs from Two Queries Together in MySQL? If you have two queries that returns the same row fields, you can merge their outputs together with the UNION operator. The following tutorial exercise shows you how to return all links that were created since year 2006 plus the o... 2017-12-21, 2287🔥, 0💬

Using Subqueries in the FROM Clause in MySQL
How To Use Subqueries in the FROM clause in MySQL? If you have a query returning many rows of data, and you want to perform another query on those rows, you can put the first query as a subquery in the FROM clause of the second query. A subquery used in this way become a temporary table, and you mus... 2017-12-21, 2225🔥, 0💬

Returning the Second 5 Rows in MySQL
How To Return the Second 5 Rows in MySQL? If you want to display query output in multiple pages with 5 rows per page, and the visitor wants to see the output for the second page, you need to display query output from row 6 to row 10. You can use the "LIMIT startRow maxRows" clause to return only row... 2017-12-21, 2222🔥, 0💬

Counting Groups Returned from GROUP BY in MySQL
How To Count Groups Returned with the GROUP BY Clause in MySQL? If you use the COUNT(*) function on groups returned with the GROUP BY clause, it will count the number of rows within each group, not the number of groups. If you want to count the number of groups, you can put the GROUP BY query into a... 2017-12-21, 2184🔥, 0💬

Managing User Accounts and Access Privileges in MySQL
Where to find answers to frequently asked questions on Managing User Accounts and Access Privileges in MySQL? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Managing User Accounts and Access Privileges in MySQL. Clear answers are provided with tu... 2017-12-13, 2583🔥, 0💬

Listing All User Accounts in MySQL
How To List All Existing User Accounts in MySQL? MySQL stores all existing user accounts in a table called "mysql.user". If you want see all user accounts, you can use the "SELECT" command as shown in the tutorial exercise below: &gt;cd \mysql\bin &gt;mysql -u root -pretneciyf mysql mysql&am... 2017-12-13, 2293🔥, 0💬

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General MySQL Oracle SQL Server