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.

SELECT CONCAT(col_A,' ', col_B) AS concat_col FROM table_name; -- Concat 2 columns

SELECT col_A || ' ' || col_B AS concat_col FROM table_name; -- Concat 2 columns

​

SELECT UPPER(col) FROM table_name; -- Turning a column into all uppercase

SELECT LOWER(col) FROM table_name; -- Turning a column into all lowercase

SELECT LEFT(col, length) FROM table_name; -- Take n no of characters from the left side of the column

SELECT RIGHT(col, length) FROM table_name; -- Take n no of characters from the right side of the column

-- Extracting Substring

SELECT SUBSTRING(col, starting_index, length) FROM table_name; -- starting_index, length are integer values

SELECT SUBSTRING(col FROM starting_index FOR POSITION('@' IN col)) FROM table_name; -- starting_index, length are integer values

SELECT SUBSTR(col, starting_index, length) FROM table_name; -- starting_index, length are integer values

SELECT REVERSE(col) FROM table_name; -- Reverse a string

SELECT CHAR_LENGTH(col) FROM table_name;  -- length of a string column

SELECT LENGTH(col) FROM table_name; -- length of a string column

SELECT POSITION('@' IN col) FROM table_name; -- position of a character in the string

SELECT STRPOS(email, '@') FROM table_name; -- position of a character in the string

SELECT REPLACE(col, 'old string', 'new string') FROM table_name; -- replacing characters

SELECT LPAD('padded', total_string_size, '#'); -- appending character from the left (####padded)

SELECT RPAD('padded', total_string_size, '#'); -- appending character from the right (padded####)

-- TRIM([leading | trailing | both] [characters] from string)

SELECT TRIM(BOTH 'x' FROM 'xxxxHelloxxxx') -- Hello

SELECT TRIM(TRAILING 'x' FROM 'xHelloxxxx') -- xHello

SELECT TRIM(LEADING 'x' FROM 'xxxxHellox') -- Hellox

​

-- Pattern matching

SELECT * FROM table_name WHERE col LIKE '_ELF%'; -- Case sensitive match

SELECT * FROM table_name WHERE col ILIKE '_ELF%'; -- Case insensitive match

SELECT * FROM table_name WHERE to_tsvector(col) @@ to_tsquery('elf'); -- Case insensitive match

​

CREATE EXTENSION IF NOT EXISTS fuzzystrmatch;

SELECT levenshtein('GUMBO', 'GAMBOL'); -- levenshtein score of similarity between 2 words

CREATE EXTENSION IF NOT EXISTS pg_trgm;

SELECT similarity('GUMBO', 'GAMBOL'); -- trigram similarity score

-- Creating a table to demonstrate the use of strings in SQL

CREATE TABLE players (

    id INT,

    name VARCHAR(100)

);

​

-- Inserting sample data

INSERT INTO players (id, name)

VALUES (1, 'John Doe'), (2, 'Jane Smith'), (3, 'Michael Johnson');

​

-- Searching for a specific string within the 'name' column using LIKE clause

SELECT * FROM players WHERE name LIKE '%Smith%';

​

-- Updating a string value

UPDATE players SET name = REPLACE(name, 'John', 'Mike') WHERE id = 1;

​

-- Concatenating strings

SELECT CONCAT('Hello', ' ', name) AS greeting FROM players WHERE id = 2;