SQL(Structured Query Language) is a domain-specific language used in programming and designed for managing data held in a relational database management system (RDBMS), or for stream processing in a relational data stream management system (RDSMS). This is a concise tldr format cheatsheet for SQL.

• DDL is short name of Data Definition Language, which deals with database schemas and descriptions, of how the data should reside in the database.

• DML is short name of Data Manipulation Language which deals with data manipulation, and includes most common SQL statements such SELECT, INSERT, UPDATE, DELETE etc, and it is used to store, modify, retrieve, delete and update data in database.

• DCL is short name of Data Control Language which includes commands such as GRANT, and mostly concerned with rights, permissions and other controls of the database system.

Datatypes

Text types

Data type	Description
CHAR(size)	Holds a fixed length string (can contain letters, numbers, and special characters). The fixed size is specified in parenthesis. Can store up to 255 characters
VARCHAR(size)	Holds a variable length string (can contain letters, numbers, and special characters). The maximum size is specified in parenthesis. Can store up to 255 characters. Note: If you put a greater value than 255 it will be converted to a TEXT type
TINYTEXT	Holds a string with a maximum length of 255 characters
TEXT	Holds a string with a maximum length of 65,535 characters
BLOB	For BLOBs (Binary Large OBjects). Holds up to 65,535 bytes of data
MEDIUMTEXT	Holds a string with a maximum length of 16,777,215 characters
MEDIUMBLOB	For BLOBs (Binary Large OBjects). Holds up to 16,777,215 bytes of data
LONGTEXT	Holds a string with a maximum length of 4,294,967,295 characters
LONGBLOB	For BLOBs (Binary Large OBjects). Holds up to 4,294,967,295 bytes of data
ENUM(x,y,z,etc.)	Let you enter a list of possible values. You can list up to 65535 values in an ENUM list. If a value is inserted that is not in the list, a blank value will be inserted.Note: The values are sorted in the order you enter them.You enter the possible values in this format: ENUM('X','Y','Z')
SET	Similar to ENUM except that SET may contain up to 64 list items and can store more than one choice

Number types

Data type	Description
TINYINT(size)	-128 to 127 normal. 0 to 255 UNSIGNED*. The maximum number of digits may be specified in parenthesis
SMALLINT(size)	-32768 to 32767 normal. 0 to 65535 UNSIGNED*. The maximum number of digits may be specified in parenthesis
MEDIUMINT(size)	-8388608 to 8388607 normal. 0 to 16777215 UNSIGNED*. The maximum number of digits may be specified in parenthesis
INT(size)	-2147483648 to 2147483647 normal. 0 to 4294967295 UNSIGNED*. The maximum number of digits may be specified in parenthesis
BIGINT(size)	-9223372036854775808 to 9223372036854775807 normal. 0 to 18446744073709551615 UNSIGNED*. The maximum number of digits may be specified in parenthesis
FLOAT(size,d)	A small number with a floating decimal point. The maximum number of digits may be specified in the size parameter. The maximum number of digits to the right of the decimal point is specified in the d parameter
DOUBLE(size,d)	A large number with a floating decimal point. The maximum number of digits may be specified in the size parameter. The maximum number of digits to the right of the decimal point is specified in the d parameter
DECIMAL(size,d)	A DOUBLE stored as a string , allowing for a fixed decimal point. The maximum number of digits may be specified in the size parameter. The maximum number of digits to the right of the decimal point is specified in the d parameter

Date types

Data type	Description
DATE()	A date. Format: YYYY-MM-DDNote: The supported range is from '1000-01-01' to '9999-12-31'
DATETIME()	*A date and time combination. Format: YYYY-MM-DD HH:MI:SSNote: The supported range is from '1000-01-01 00:00:00' to '9999-12-31 23:59:59'
TIMESTAMP()	*A timestamp. TIMESTAMP values are stored as the number of seconds since the Unix epoch ('1970-01-01 00:00:00' UTC). Format: YYYY-MM-DD HH:MI:SSNote: The supported range is from '1970-01-01 00:00:01' UTC to '2038-01-09 03:14:07' UTC
TIME()	A time. Format: HH:MI:SSNote: The supported range is from '-838:59:59' to '838:59:59'
YEAR()	A year in two-digit or four-digit format.Note: Values allowed in four-digit format: 1901 to 2155. Values allowed in two-digit format: 70 to 69, representing years from 1970 to 2069

Database

• Create

  create database dbname;
  

• Drop

  drop database dbname;
  

Table

• Check if not exit and create

  IF OBJECT_ID('tbl_kunde', N'U') is not null
  	drop table tbl_kunde;
  GO
  create table tbl_kunde (
    id_kunde int not null primary key,
    fi_moral_nr int,
    name varchar(25) not null,
    vorname varchar not null,
    wohnort varchar
  );
  GO
  

Alter Table

• Primary Key

  ALTER TABLE tbl_kunde ADD PRIMARY KEY (id_kunde);
  

• Foreign Key

  ALTER TABLE tbl_kunde ADD CONSTRAINT FK_fi_moral_nr FOREIGN KEY (fi_moral_nr)
    REFERENCES tkey_moral
    ON UPDATE CASCADE
    ON DELETE SET NULL;
  

• Constraint

  ALTER TABLE tkey_moral ADD CONSTRAINT PK_id_moral_nr PRIMARY KEY (id_moral_nr);
  ALTER TABLE tbl_kunde ADD CONSTRAINT FK_fi_moral_nr FOREIGN KEY (fi_moral_nr)
    REFERENCES tkey_moral
    ON UPDATE CASCADE
    ON DELETE SET NULL;
  

Insert

• Selected fields

  insert into tkey_moral (id_moral_nr, moral_bez) values (1, 'gut'), (2, 'schlecht'), (3, 'schlecht');
  

• All fields

  INSERT INTO tbl_kunde VALUES (3838,1,'Meier','Laura','Waldibrücke')
  

Update

• Update by condition

  update tbl_kunde set name = 'Menzer' where name = 'Waltenspühl-Menzer'
  update tass_police set praem_stufe = 101 where praem_stufe = 108
  

Delete

• All

  delete from tbl_kunde
  

• Condition

  delete from tkey_moral where id_moral_nr = 4
  delete from tbl_kunde where vorname = 'Peter' and name = 'Fischer' or vorname = 'Martin' and name = 'Müller'
  

Index

• Create

  create unique index ix_kund_name on tbl_kunde (name)
  

• Disable

  alter index ix_kund_name on tbl_kunde disable
  

• Rebuild

  alter index ix_kund_name on tbl_kunde rebuild
  

• Reorganize

  alter index ix_kund_name on tbl_kunde reorganize
  

• Drop

  drop index ix_kund_name on tbl_kunde
  

• Alter

  drop index ix_kund_name on tbl_kunde
  

Type

• create

  create type tp_moralisches from numeric(9,0)
  

Login

• change password

  alter login stud23 with password = 'hello' old_password = 'pass_wd23'
  

User

• create

  create user romulus from login romulus
  

• drop

  drop user romulus
  

Grant/ Revoke

• Grant rights

  grant select, insert, delete, references, update to romulus
  

• Grant refrences

  grant references (id_moral_nr) on tkey_moral to romulus
  

• Revoke

  revoke insert, delete, references, update to romulus
  

Role

• Create

  create role verkauf
  

• Add member

  exec sp_addrolemember 'verkauf', 'anna'
  

Grant Role

• Grant rights

  grant select, update, insert, delete on tbl_kunde to verkauf
  

View

• Create detailed

  CREATE VIEW v_kunden (id, name, vorname, ort, police, gebiet) AS
    SELECT k.id_kunde, k.name, k.vorname, k.wohnort, v.vers_bez,
           v.vers_gebiet
      FROM tbl_kunde AS k, tkey_versicherung AS v, tass_police AS p
        WHERE k.id_kunde = p.id_fi_kunde
          AND p.id_fi_vers_art = v.id_vers_art;
  

• Create simple

  create view plain as select id_kunde, name, vorname from tbl_kunde
  

• Create advanced

  create view v_umsatz as select sum(cast(bezahlt as float)) as 'Umsatz aus Policen' from tass_police
  

Select

• Basic

  select dt_jahr from dbo.tbl_stueck
  

• Condition

  select dt_jahr from dbo.tbl_stueck where dt_jahr is not null
  

• Order

  select dt_jahr from dbo.tbl_stueck
  where dt_jahr is not null
  order by dt_jahr desc
  

• Distinct

  select distinct dt_jahr from dbo.tbl_stueck
  where dt_jahr is not null
  order by dt_jahr asc
  

• And Condition

  select * from tbl_stueck where dt_jahr = 1970 and dt_zeit > 3
  

• Between

  select * from tbl_stueck where dt_jahr = 1970 and dt_zeit between 3 and 10
  

• Like

  select * from tbl_stueck where dt_stueck_titel like 'Let%'
  

• Count

  select count(dt_stueck_titel) from tbl_stueck where dt_stueck_titel like 'Let%'
  

• Having and without join

  select i.dt_name, count(s.dt_stueck_titel) from tbl_stueck as s, tkey_interpret as i
  where  s.fi_interpret = i.id_interpret
  group by i.dt_name
  having count(s.dt_stueck_titel) >10
  order by count(s.dt_stueck_titel) de
  

Join the hard way

• Inner Join

  select s.dt_stueck_titel, i.dt_name
  from tbl_stueck as s, tkey_interpret as i
  where  s.fi_interpret = i.id_interpret
  order by s.dt_stueck_titel
  

• Multi Join

  select sa.id_jahr, st.dt_stueck_titel, ip.dt_name
  from tbl_stueck as st, tass_stueck_sampler as ss, tkey_sampler as sa, tkey_interpret as ip
  where ss.id_fi_stueck_nr = st.id_stueck_nr 
  and ss.id_fi_jahr = sa.id_jahr
  and  st.fi_interpret = ip.id_interpret
  order by  st.dt_stueck_titel
  

Join the right way

• Inner Equi Key Joining

  select dt_stueck_titel, dt_name
  from tbl_stueck join tkey_interpret 
  on fi_interpret = id_interpret
  order by dt_stueck_titel
  

• Multi Inner Equi Key Joining

  select id_fi_jahr, dt_stueck_titel, dt_name
  from tbl_stueck
  join tass_stueck_sampler on id_fi_stueck_nr = id_stueck_nr
  join tkey_interpret on fi_interpret = id_interpret
  order by  dt_stueck_titel
  

About Joins

SELECT customers.id, customers.name, items.name, customers.state 
FROM customers, items
WHERE customers.id=seller_id
ORDER BY customers.id

Join tables -> Joining two tables together in a query output. The third line is important because it shows how the two tables are related (in this case it is their key values).

SELECT customers.name, items.name FROM customers
LEFT OUTER JOIN items ON customers.id=seller_id

LEFT/RIGHT OUTER JOIN -> Takes the table left of the word 'LEFT' or 'RIGHT' (in this case customers) and joins it regardless of whether it has any values or not. So the above statement shows all users/customers, even if they aren't selling anything.

Select with Subqueries

• Select max and min values

  select dt_stueck_titel as Titel, dt_zeit as Zeit
  from tbl_stueck
  where dt_zeit = (select max(dt_zeit) from tbl_stueck)
  or dt_zeit = (select min(dt_zeit) from tbl_stueck)
  order by dt_zeit;
  

• Select with query in condition

  select dt_stueck_titel as Titel, dt_zeit as Zeit
  from tbl_stueck
  where dt_zeit between (select avg(dt_zeit) from tbl_stueck)*0.9
  and (select avg(dt_zeit) from tbl_stueck)*1.1
  order by dt_zeit;
  

• Select query as value

  select dt_stueck_titel as Titel,
  dt_zeit/(select avg(dt_zeit) from tbl_stueck)*100 as Zeit
  from tbl_stueck
  where dt_stueck_titel = 'You Shook Me'
  

Union

• Unify two result sets with a condition

  select *  from
  (select dt_stueck_titel as titel, 'stück' as 'type' from tbl_stueck
  union
  select dt_name as titel,  'inter' as 'type' from tkey_interpret
  union
  select dt_stao as titel,  'stao' as 'type' from tkey_standort) as t
  where t.titel like '%boy%'
  

Transactions

• Run a transaction

  begin transaction
  update tass_police set bezahlt = 0 where id_fi_kunde = 3533 and id_fi_vers_art = 1700
  commit
  -- or rollback
  

Function

A function can be called from inside a statement just like any other function and can return a scalar value.

• Create - Get value from table

  create function f_plic_bez()
    returns decimal(10,2)
    as begin
    return (select sum(bezahlt) from tass_police)
    end;
  go
  select  dbo.f_plic_bez() AS 'Summe aller bezahlten Leistungen'
  go
  

• Drop

  drop function f_bezahlt_versich
  

• Create - With parameters

  create function f_rabatt(@name varchar(40), @vers varchar(30))
    returns int
    as begin
    return (select (praem_stufe-100)*10 from  tass_police
    join tbl_kunde on id_fi_kunde = id_kunde
    join tkey_versicherung on id_fi_vers_art = id_vers_art
    where name = @name and vers_bez = @vers)
    end
  

Procedure

Stored procedures are stored as precompilated code (stored routine) and called by the programmer wherever it wants to fire. Stored procedure can return value(s).

• Create and execute

  CREATE PROCEDURE p_polic_del @fname VARCHAR(30), @versich VARCHAR(30)
    AS
    BEGIN
      DELETE FROM tass_police
        FROM tbl_kunde, tkey_versicherung
          WHERE name = @fname
            AND id_kunde = id_fi_kunde
            AND id_fi_vers_art = id_vers_art
            AND vers_bez = @versich
      IF @@ROWCOUNT = 0
        PRINT 'Police existiert nicht.'
        ELSE PRINT 'Löschung vollzogen.'
    END
  GO
  
  EXECUTE p_polic_del 'Meier', 'Taggeld';
  

Variables

• Declare

  DECLARE @veraenderung SMALLINT = 180;
  DECLARE @neue_summe INT;
  

Trigger

Triggers are named database objects fired automatically when insert, delete, update (or other event) occurred, there can be no explicit invocation. Trigger can not return any data.

• Create simple

  create trigger t_ort on tbl_kunde
    after insert, update
    as beginn
      set @ort = select wohnort from inserted)
      if((@ort like '/^[A-Z]') && len(@ort) < 2)
        rollback transaction
    end
  end
  

• Drop

  drop trigger t_ort
  

• Checks the referential integrity

  create trigger t_bst_mut on bst
  	for insert, update
  	as
  	begin
  		set nocount on;
  		if(select id_fi_k from inserted) NOT IN (select id_kund from knd)
  			begin
  				raiserror('Es besteht kein entsprechender Kunde.', 15, 1);
  				rollback transaction;
  			end
  	end;
  

• Replaces on delete no action

  create trigger t_ku_del on knd
  	for delete
  	as
  	begin
  		set nocount on;
  		if((select id_kunde from deleted) IN (select id_fi_k from bst))
  			begin
  				raiserror('Löschung verwert; es bestehen noch Bestelungen für diesen Kunden.', 15, 1)
  				rollback transaction
  			end
  	end;
  

• Replaces on update cascade

  create trigger t_update_knd on knd
  	after update
  	as
  	begin
  		set nocount on;
  		update bst set id_fi_k = (select id_kund from inserted)
  	end;
  

• Replaces on delete cascade

  create trigger t_delete_knd on knd
  	after delete
  	as
  	begin
  		delete from bst where id_fi_k = (select id_kund from deleted)
  	end;