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| author | Adam Bard <adam@adambard.com> | 2018-11-04 09:26:31 -0800 | 
|---|---|---|
| committer | Adam Bard <adam@adambard.com> | 2018-11-04 09:26:31 -0800 | 
| commit | eabb26c70eb207d98ebf5e14e8f1d94dfeb61c76 (patch) | |
| tree | 3755509a29213780782ad1d68ec11154b46365d7 | |
| parent | deef75b16e50b8d8c31c001003712b950daebf74 (diff) | |
Use dash commenting on sql doc instead
| -rw-r--r-- | sql.html.markdown | 82 | 
1 files changed, 41 insertions, 41 deletions
| diff --git a/sql.html.markdown b/sql.html.markdown index 0638a731..200f4f98 100644 --- a/sql.html.markdown +++ b/sql.html.markdown @@ -13,93 +13,93 @@ Several of these sample commands assume that the [MySQL employee sample database  ```sql -# Comments start with a pound sign. End each command with a semicolon. +-- Comments start with two hyphens. End each command with a semicolon. -# SQL is not case-sensitive about keywords. The sample commands here -# follow the convention of spelling them in upper-case because it makes  -# it easier to distinguish them from database, table, and column names. +-- SQL is not case-sensitive about keywords. The sample commands here +-- follow the convention of spelling them in upper-case because it makes  +-- it easier to distinguish them from database, table, and column names. -# Create and delete a database. Database and table names are case-sensitive. +-- Create and delete a database. Database and table names are case-sensitive.  CREATE DATABASE someDatabase;  DROP DATABASE someDatabase; -# List available databases. +-- List available databases.  SHOW DATABASES; -# Use a particular existing database.  +-- Use a particular existing database.   USE employees;     -# Select all rows and columns from the current database's departments table. -# Default activity is for the interpreter to scroll the results on your screen.  +-- Select all rows and columns from the current database's departments table. +-- Default activity is for the interpreter to scroll the results on your screen.   SELECT * FROM departments; -# Retrieve all rows from the departments table,  -# but only the dept_no and dept_name columns.  -# Splitting up commands across lines is OK. +-- Retrieve all rows from the departments table,  +-- but only the dept_no and dept_name columns.  +-- Splitting up commands across lines is OK.  SELECT dept_no,         dept_name FROM departments; -# Retrieve all departments columns, but just 5 rows.  +-- Retrieve all departments columns, but just 5 rows.   SELECT * FROM departments LIMIT 5; -# Retrieve dept_name column values from the departments -# table where the dept_name value has the substring "en".  +-- Retrieve dept_name column values from the departments +-- table where the dept_name value has the substring "en".   SELECT dept_name FROM departments WHERE dept_name LIKE "%en%"; -# Retrieve all columns from the departments table where the dept_name -# column starts with an "S" and has exactly 4 characters after it.  +-- Retrieve all columns from the departments table where the dept_name +-- column starts with an "S" and has exactly 4 characters after it.   SELECT * FROM departments WHERE dept_name LIKE "S____"; -# Select title values from the titles table but don't show duplicates. +-- Select title values from the titles table but don't show duplicates.  SELECT DISTINCT title FROM titles; -# Same as above, but sorted (case-sensitive) by the title values.  +-- Same as above, but sorted (case-sensitive) by the title values.   SELECT DISTINCT title FROM titles ORDER BY title; -# Show the number of rows in the departments table. +-- Show the number of rows in the departments table.  SELECT COUNT(*) FROM departments; -# Show the number of rows in the departments table that -# have "en" as a substring of the dept_name value.  +-- Show the number of rows in the departments table that +-- have "en" as a substring of the dept_name value.   SELECT COUNT(*) FROM departments WHERE dept_name LIKE "%en%"; -# A JOIN of information from multiple tables: the titles table shows  -# who had what job titles, by their employee numbers, from what  -# date to what date. Retrieve this information, but instead of the -# employee number, use the employee number as a cross-reference to  -# the employees table to get each employee's first and last name -# instead. (And only get 10 rows.) +-- A JOIN of information from multiple tables: the titles table shows  +-- who had what job titles, by their employee numbers, from what  +-- date to what date. Retrieve this information, but instead of the +-- employee number, use the employee number as a cross-reference to  +-- the employees table to get each employee's first and last name +-- instead. (And only get 10 rows.)  SELECT employees.first_name, employees.last_name,         titles.title, titles.from_date, titles.to_date  FROM titles INNER JOIN employees ON         employees.emp_no = titles.emp_no LIMIT 10; -# List all the tables in all the databases. Implementations typically provide -# their own shortcut command to do this with the database currently in use. +-- List all the tables in all the databases. Implementations typically provide +-- their own shortcut command to do this with the database currently in use.  SELECT * FROM INFORMATION_SCHEMA.TABLES  WHERE TABLE_TYPE='BASE TABLE'; -# Create a table called tablename1, with the two columns shown, for -# the database currently in use. Lots of other options are available -# for how you specify the columns, such as their datatypes. +-- Create a table called tablename1, with the two columns shown, for +-- the database currently in use. Lots of other options are available +-- for how you specify the columns, such as their datatypes.  CREATE TABLE tablename1 (`fname` VARCHAR(20),`lname` VARCHAR(20)); -# Insert a row of data into the table tablename1. This assumes that the  -# table has been defined to accept these values as appropriate for it.  +-- Insert a row of data into the table tablename1. This assumes that the  +-- table has been defined to accept these values as appropriate for it.   INSERT INTO tablename1 VALUES('Richard','Mutt'); -# In tablename1, change the fname value to "John" -# for all rows that have an lname value of "Mutt".  +-- In tablename1, change the fname value to "John" +-- for all rows that have an lname value of "Mutt".   UPDATE tablename1 SET fname="John" WHERE lname="Mutt"; -# Delete rows from the tablename1 table -# where the lname value begins with "M". +-- Delete rows from the tablename1 table +-- where the lname value begins with "M".  DELETE FROM tablename1 WHERE lname like "M%"; -# Delete all rows from the tablename1 table, leaving the empty table. +-- Delete all rows from the tablename1 table, leaving the empty table.  DELETE FROM tablename1; -# Remove the entire tablename1 table.  +-- Remove the entire tablename1 table.   DROP TABLE tablename1;  ``` | 
