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SQL - Coggle Diagram

- - - - ADD -- Adds a new column to an existing table
      - ADD CONSTRAINT -- Creates a new constraint on an existing table, which is used to specify rules for any data in the table.
      - ALTER TABLE -- Adds, deletes or edits columns in a table. It can also be used to add and delete constraints in a table, as per the above.
      - ALTER COLUMN -- Changes the data type of a table’s column.
      - ALL -- Returns true if all of the subquery values meet the passed condition.
      - AND -- Used to join separate conditions within a WHERE clause.
      - ANY -- Returns true if any of the subquery values meet the given condition.
      - AS -- Renames a table or column with an alias value which only exists for the duration of the query.
      - ASC -- Used with ORDER BY to return the data in ascending order.
      - BETWEEN -- Selects values within the given range.
      - CASE -- Changes query output depending on conditions.
      - CHECK -- Adds a constraint that limits the value which can be added to a column.
      - CREATE DATABASE -- Creates a new database.
      - CREATE TABLE -- Creates a new table.
      - DEFAULT -- Sets a default value for a column
      - DELETE -- Delete data from a table.
      - DESC -- Used with ORDER BY to return the data in descending order.
      - DROP COLUMN -- Deletes a column from a table.
      - DROP DATABASE -- Deletes the entire database.
      - DROP DEAFULT -- Removes a default value for a column.
      - DROP TABLE -- Deletes a table from a database.
      - EXISTS -- Checks for the existence of any record within the subquery, returning true if one or more records are returned.
      - FROM -- Specifies which table to select or delete data from.
      - IN -- Used alongside a WHERE clause as a shorthand for multiple OR conditions.
      - INSERT INTO -- Adds new rows to a table.
      - IS NULL -- Tests for empty (NULL) values.
      - IS NOT NULL -- The reverse of NULL. Tests for values that aren’t empty / NULL.
      - LIKE -- Returns true if the operand value matches a pattern.
      - NOT -- Returns true if a record DOESN’T meet the condition.
      - OR -- Used alongside WHERE to include data when either condition is true.
      - ORDER BY -- Used to sort the result data in ascending (default) or descending order through the use of ASC or DESC keywords.
      - ROWNUM -- Returns results where the row number meets the passed condition.
      - SELECT -- Used to select data from a database, which is then returned in a results set.
      - SELECT DISTINCT -- Sames as SELECT, except duplicate values are excluded.
      - SELECT INTO -- Copies data from one table and inserts it into another.
      - SELECT TOP -- Allows you to return a set number of records to return from a table.
      - SET -- Used alongside UPDATE to update existing data in a table.
      - SOME -- Identical to ANY.
      - TOP -- Used alongside SELECT to return a set number of records from a table.
      - TRUNCATE TABLE -- Similar to DROP, but instead of deleting the table and its data, this deletes only the data.
      - UNION -- Combines the results from 2 or more SELECT statements and returns only distinct values.
      - UNION ALL -- The same as UNION, but includes duplicate values.
      - UNIQUE -- This constraint ensures all values in a column are unique.
      - UPDATE -- Updates existing data in a table.
      - VALUES -- Used alongside the INSERT INTO keyword to add new values to a table.
      - WHERE -- Filters results to only include data which meets the given condition.
  - - - ALL TRUE if all of the subquery values meet the condition
        
        AND TRUE if all the conditions separated by AND is TRUE
        
        ANY TRUE if any of the subquery values meet the condition
        
        BETWEEN TRUE if the operand is within the range of comparisons
        
        EXISTS TRUE if the subquery returns one or more records
        
        IN TRUE if the operand is equal to one of a set of expressions
        
        LIKE TRUE if the operand matches a pattern
        
        NOT Displays a record if the condition(s) is NOT TRUE
        
        OR TRUE if any of the conditions separated by OR is TRUE
        
        SOME TRUE if any of the subquery values meet the condition
  - - - inner - in mysql it is implicit, i.e. simply writing join will give inner join, returns rows for which key is present in both,
        e.x. select * from dept join emp on dept.deptno=emp.deptno;
      - outer - has no purpose in mysql other than backward compatibility
      - left join - will give result of inner join + any rows in left with key value which was not in right.
        e.x. select * from dept left join emp on dept.deptno=emp.deptno;
      - right join - will give resutlt of inner join + any rows in right with key value which was not in left. e.x. select * from dept right join emp on dept.deptno=emp.deptno;
      - anti joins - returns any rows with keys not in inner joins. done using join and null condition. refer links for code
        
        - left anti join
        
        - right anti join
        
        - full anti join
      - full join - mysql does not suppor full outer join, it is implemented using 'union' between left join and right join. in case 'union all' is used. one of the left or right joins must be anti join. this is because union gives distinct values, where as union all gives duplicates as well.
      - self join - when there is self relation in a table, for example when a table contains employees of an hierarchical organization. with column containing employee id of managers of that employee. e.x. select e.empno, m.empno as mgrid from emp e inner join emp m on e.mgr=m.empno;
- - - - Rollback -
        
        Used on transaction failure. DDL cant be rolled backed, simple rollback will rollback all changes post START TRANSACTION command.
        
        ROLLBACK or ROLLBACK TO savepoint_name;
      - commit - changes are committed to storage. till commit, changes are only in RAM, on success transaction is commited.
      - SAVEPOINT name; creates savepoint, which can be rolled back to using rolllback command
      - related concepts
        
        ROW LOCKING - if other user tries to edit same row which was edited by this user after start of transaction, other users cmd/query will hang till end of this users transaction(and may timeout error if this transaction takes too much time). this is because sql transactions are atomic in nature
        
        if table does not contain primary key then entire table is locked instead of row, during any transaction.
        
        To lock a different row after starting transaction use - select ..... for update/delete. e.x. select * from emp where id=3 for update; //now this row will be locked, even though it is not updated yet. This is called pessimistic lock.
        
        by default all queries are transactions and auto commit is fired on each query.
        
        Commands - START TRANSACTION, ROLLBACK, SAVEPOINT, COMMIT
        
        ACID Properties
        
        A - Atomicity
        
        DML opertaions will either be successfull/Failure. Partial transactions are never commited. transactions are atomic
        
        C - Consistency
        
        At the end of transaction same state will be visible to all the users.
        
        I - Isolation
        
        Every transaction is isolated from each other. other user cant see my transaction changes until its committed.
        
        D - Durability
        
        Persistent and non volatile - At the end of transaction the state will be saved on to the server.
  - - - INSERT
        
        INSERT (multi-table)
        
        MERGE
        
        UPDATE
        
        DELETE
    - - COPY INTO <table> (loading/importing data)
        
        COPY INTO <location> (unloading/exporting data)
        
        VALIDATE (table function)
        
        PUT
        
        GET
        
        LIST (can also be used with named external stages)
        
        REMOVE
  - - - Grant
        
        GRANT ALL PRIVILEGES ON database/database.tablename to name/name@host;
        
        GRANT CLAUSE1, CLAUSE2, CLAUSE3 ON database/database.tablename to name/name@host;
      - Revoke
        
        REVOKE ALL PRIVILEGES / CLAUSE1, CLAUSE2 ... .. ON database/database.table from name/name@host
      - user management
        
        CREATE USER name IDENTIFIED BY password
        
        drop user name;
        
        mysql -u name -ppassword or mysql -u name -p
  - - - ALTER <object>
      - COMMENT
      - CREATE <object>
      - DESCRIBE <object>
      - DROP <object>
      - SHOW <objects>
      - USE <object>
      - TRUNCATE TABLE
- - - - ASCII -- Returns the equivalent ASCII value for a specific character.
      - CHAR_LENGTH -- Returns the character length of a string.
      - CHARACTER_LENGTH -- Same as CHAR_LENGTH.
      - CONCAT -- Adds expressions together, with a minimum of 2.
      - CONCAT_WS -- Adds expressions together, but with a separator between each value.
      - FIELD -- Returns an index value relative to the position of a value within a list of values.
      - FIND IN SET -- Returns the position of a string in a list of strings.
      - FORMAT -- When passed a number, returns that number formatted to include commas (eg 3,400,000).
      - INSERT -- Allows you to insert one string into another at a certain point, for a certain number of characters.
      - INSTR -- Returns the position of the first time one string appears within another.
      - LCASE -- Converts a string to lowercase.
      - LEFT -- Starting from the left, extracts the given number of characters from a string and returns them as another.
      - LENGTH -- Returns the length of a string, but in bytes.
      - LOCATE -- Returns the first occurrence of one string within another,
      - LOWER -- Same as LCASE.
      - LPAD -- Left pads one string with another, to a specific length.
      - LTRIM -- Removes any leading spaces from the given string.
      - MID -- Extracts one string from another, starting from any position.
      - POSITION -- Returns the position of the first time one substring appears within another.
      - REPEAT -- Allows you to repeat a string
      - REPLACE -- Allows you to replace any instances of a substring within a string, with a new substring.
      - REVERSE -- Reverses the string.
      - RIGHT -- Starting from the right, extracts the given number of characters from a string and returns them as another.
      - RPAD -- Right pads one string with another, to a specific length.
      - RTRIM -- Removes any trailing spaces from the given string.
      - SPACE -- Returns a string full of spaces equal to the amount you pass it.
      - STRCMP -- Compares 2 strings for differences
      - SUBSTR -- Extracts one substring from another, starting from any position.
      - SUBSTRING -- Same as SUBSTR
      - SUBSTRING_INDEX -- Returns a substring from a string before the passed substring is found the number of times equals to the passed number.
      - TRIM -- Removes trailing and leading spaces from the given string. Same as if you were to run LTRIM and RTRIM together.
      - UCASE -- Converts a string to uppercase.
      - UPPER -- Same as UCASE.
  - - - ABS -- Returns the absolute value of the given number.
      - ACOS -- Returns the arc cosine of the given number.
      - ASIN -- Returns the arc sine of the given number.
      - ATAN -- Returns the arc tangent of one or 2 given numbers.
      - ATAN2 -- Returns the arc tangent of 2 given numbers.
      - AVG -- Returns the average value of the given expression.
      - CEIL -- Returns the closest whole number (integer) upwards from a given decimal point number.
      - CEILING -- Same as CEIL.
      - COS -- Returns the cosine of a given number.
      - COT -- Returns the cotangent of a given number.
      - COUNT -- Returns the amount of records that are returned by a SELECT query.
      - DEGREES -- Converts a radians value to degrees.
      - DIV -- Allows you to divide integers.
      - EXP -- Returns e to the power of the given number.
      - FLOOR -- Returns the closest whole number (integer) downwards from a given decimal point number.
      - GREATEST -- Returns the highest value in a list of arguments.
      - LEAST -- Returns the smallest value in a list of arguments.
      - LN -- Returns the natural logarithm of the given number.
      - LOG -- Returns the natural logarithm of the given number, or the logarithm of the given number to the given base.
      - LOG10 -- Does the same as LOG, but to base 10.
      - LOG2 -- Does the same as LOG, but to base 2.
      - MAX -- Returns the highest value from a set of values.
      - MIN -- Returns the lowest value from a set of values.
      - MOD -- Returns the remainder of the given number divided by the other given number.
      - PI -- Returns PI.
      - POW -- Returns the value of the given number raised to the power of the other given number.
      - POWER -- Same as POW.
      - RADIANS -- Converts a degrees value to radians.
      - RAND -- Returns a random number.
      - ROUND -- Rounds the given number to the given amount of decimal places.
      - SIGN -- Returns the sign of the given number.
      - SIN -- Returns the sine of the given number.
      - SQRT -- Returns the square root of the given number.
      - SUM -- Returns the value of the given set of values combined.
      - TAN -- Returns the tangent of the given number.
      - TRUNCATE -- Returns a number truncated to the given number of decimal places.
  - - - ADDDATE -- Adds a date interval (eg: 10 DAY) to a date (eg: 20/01/20) and returns the result (eg: 20/01/30).
      - ADDTIME -- Adds a time interval (eg: 02:00) to a time or datetime (05:00) and returns the result (07:00).
      - CURDATE -- Gets the current date.
      - CURRENT_DATE -- Same as CURDATE.
      - CURRENT_TIME -- Gest the current time.
      - CURRENT_TIMESTAMP -- Gets the current date and time.
      - CURTIME -- Same as CURRENT_TIME.
      - DATE -- Extracts the date from a datetime expression.
      - DATEDIFF -- Returns the number of days between the 2 given dates.
      - DATE_ADD -- Same as ADDDATE.
      - DATE_FORMAT -- Formats the date to the given pattern.
      - DATE_SUB -- Subtracts a date interval (eg: 10 DAY) to a date (eg: 20/01/20) and returns the result (eg: 20/01/10).
      - DAY -- Returns the day for the given date.
      - DAYNAME -- Returns the weekday name for the given date.
      - DAYOFWEEK -- Returns the index for the weekday for the given date.
      - DAYOFYEAR -- Returns the day of the year for the given date.
      - EXTRACT -- Extracts from the date the given part (eg MONTH for 20/01/20 = 01).
      - FROM DAYS -- Returns the date from the given numeric date value.
      - HOUR -- Returns the hour from the given date.
      - LAST DAY -- Gets the last day of the month for the given date.
      - LOCALTIME -- Gets the current local date and time.
      - LOCALTIMESTAMP -- Same as LOCALTIME.
      - MAKEDATE -- Creates a date and returns it, based on the given year and number of days values.
      - MAKETIME -- Creates a time and returns it, based on the given hour, minute and second values.
      - MICROSECOND -- Returns the microsecond of a given time or datetime.
      - MINUTE -- Returns the minute of the given time or datetime.
      - MONTH -- Returns the month of the given date.
      - MONTHNAME -- Returns the name of the month of the given date.
      - NOW -- Same as LOCALTIME.
      - PERIOD_ADD -- Adds the given number of months to the given period.
      - PERIOD_DIFF -- Returns the difference between 2 given periods.
      - QUARTER -- Returns the year quarter for the given date.
      - SECOND -- Returns the second of a given time or datetime.
      - SEC_TO_TIME -- Returns a time based on the given seconds.
      - STR_TO_DATE -- Creates a date and returns it based on the given string and format.
      - SUBDATE -- Same as DATE_SUB.
      - SUBTIME -- Subtracts a time interval (eg: 02:00) to a time or datetime (05:00) and returns the result (03:00).
      - SYSDATE -- Same as LOCALTIME.
      - TIME -- Returns the time from a given time or datetime.
      - TIME_FORMAT -- Returns the given time in the given format.
      - TIME_TO_SEC -- Converts and returns a time into seconds.
      - TIMEDIFF -- Returns the difference between 2 given time/datetime expressions.
      - TIMESTAMP -- Returns the datetime value of the given date or datetime.
      - TO_DAYS -- Returns the total number of days that have passed from ‘00-00-0000’ to the given date.
      - WEEK -- Returns the week number for the given date.
      - WEEKDAY -- Returns the weekday number for the given date.
      - WEEKOFYEAR -- Returns the week number for the given date.
      - YEAR -- Returns the year from the given date.
      - YEARWEEK -- Returns the year and week number for the given date.
  - - - BIN -- Returns the given number in binary.
      - BINARY -- Returns the given value as a binary string.
      - CAST -- Converst one type into another.
      - COALESCE -- From a list of values, returns the first non-null value.
      - CONNECTION_ID -- For the current connection, returns the unique connection ID.
      - CONV -- Converts the given number from one numeric base system into another.
      - CONVERT -- Converts the given value into the given datatype or character set.
      - CURRENT_USER -- Returns the user and hostname which was used to authenticate with the server.
      - DATABASE -- Gets the name of the current database.
      - GROUP BY -- Used alongside aggregate functions (COUNT, MAX, MIN, SUM, AVG) to group the results.
      - HAVING -- Used in the place of WHERE with aggregate functions.
      - IF -- If the condition is true it returns a value, otherwise it returns another value.
      - IFNULL -- If the given expression equates to null, it returns the given value.
      - ISNULL -- If the expression is null, it returns 1, otherwise returns 0.
      - LAST_INSERT_ID -- For the last row which was added or updated in a table, returns the auto increment ID.
      - NULLIF -- Compares the 2 given expressions. If they are equal, NULL is returned, otherwise the first expression is returned.
      - SESSION_USER -- Returns the current user and hostnames.
      - SYSTEM_USER -- Same as SESSION_USER.
      - USER -- Same as SESSION_USER.
      - VERSION -- Returns the current version of the MySQL powering the databa