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Description
The SQL UNION ALL operator is used to combine
the result sets of 2 or more SELECT statements. It returns all rows from
the query (even if the row exists in more than one of the SELECT
statements). Each SELECT statement within the UNION ALL must have the same number of fields in the result sets with similar data types.
Description
The SQL UNION operator is used to combine the
result sets of 2 or more SELECT statements. It removes duplicate rows
between the various SELECT statements. Each SELECT statement within the UNION must have the same number of fields in the result sets with similar data types.
Description
The SQL EXISTS condition is used in
combination with a subquery and is considered to be met, if the subquery
returns at least one row. It can be used in a SELECT, INSERT, UPDATE,
or DELETE statement.
Description
SQL JOINS are used to retrieve data from multiple tables. A SQL JOIN is performed whenever two or more tables are joined in a SQL statement.There are 4 different types of SQL joins:
- SQL INNER JOIN (or sometimes called simple join)
- SQL LEFT OUTER JOIN (or sometimes called LEFT JOIN)
- SQL RIGHT OUTER JOIN (or sometimes called RIGHT JOIN)
- SQL FULL OUTER JOIN (or sometimes called FULL JOIN)
Description
The SQL ORDER BY clause is used to sort the records in the result set for a SELECT statement.Description
The SQL MIN function is used to return the minimum value of an expression in a SELECT statement.Description
The SQL MAX function is used to return the maximum value of an expression in a SELECT statement.Description
The SQL AVG function is used to return the average of an expression in a SELECT statement.Description
The SQL SUM function is used to return the sum of an expression in a SELECT statement.Description
The SQL SELECT statement is used to retrieve records from one or more tables in your SQL database.Description
The SQL GROUP BY clause can be used in a SELECT statement to collect data across multiple records and group the results by one or more columns.Description
SQL ALIASES can be used to create a temporary name for columns or tables.- COLUMN ALIASES are used to make column headings in your result set easier to read.
- TABLE ALIASES are used to shorten your SQL to make it easier to read or when you are performing a self join (ie: listing the same table more than once in the FROM clause).
Description
The SQL DISTINCT clause is used to remove duplicates from the result set of a SELECT statement.
