sql cheat sheet

# Finding Data Queries

# SELECT: used to select data from a database
SELECT * FROM table_name;

# DISTINCT: filters away duplicate values and returns rows of specified column
SELECT DISTINCT column_name;

# WHERE: used to filter records/rows
SELECT column1, column2 FROM table_name WHERE condition;
SELECT * FROM table_name WHERE condition1 AND condition2;
SELECT * FROM table_name WHERE condition1 OR condition2;
SELECT * FROM table_name WHERE NOT condition;
SELECT * FROM table_name WHERE condition1 AND (condition2 OR condition3);
SELECT * FROM table_name WHERE EXISTS (SELECT column_name FROM table_name WHERE condition);

# ORDER BY: used to sort the result-set in ascending or descending order
SELECT * FROM table_name ORDER BY column;
SELECT * FROM table_name ORDER BY column DESC;
SELECT * FROM table_name ORDER BY column1 ASC, column2 DESC;
SELECT TOP: used to specify the number of records to return from top of table
SELECT TOP number columns_names FROM table_name WHERE condition;
SELECT TOP percent columns_names FROM table_name WHERE condition;

# Not all database systems support SELECT TOP. The MySQL equivalent is the LIMIT clause
SELECT column_names FROM table_name LIMIT offset, count;

# LIKE: operator used in a WHERE clause to search for a specific pattern in a column
# % (percent sign) is a wildcard character that represents zero, one, or multiple characters
# _ (underscore) is a wildcard character that represents a single character
SELECT column_names FROM table_name WHERE column_name LIKE pattern;

LIKE ‘a%’ # (find any values that start with “a”)
LIKE ‘%a’ # (find any values that end with “a”)
LIKE ‘%or%’ # (find any values that have “or” in any position)
LIKE ‘_r%’ # (find any values that have “r” in the second position)
LIKE ‘a_%_%’ # (find any values that start with “a” and are at least 3 characters in length)
LIKE ‘[a-c]%’ # (find any values starting with “a”, “b”, or “c”

# See more in the source link