As used herein, it is Oracle 10g database, using the PL / SQL Developer integrated development environment (installation can be self Baidu)
the Oracle Database ---> database instance ---> tablespaces (logical units) (user) ---> Data File (physical units)
can be interpreted as below
the Earth ---> a country ---> provinces (logical unit) (citizen) ---> mountains and rivers (physical units)
typically, Oracle database will be only one instance ORCL,
create a new project:
MYSQL: create a database, create a corresponding table
Oracle: create a table space, create users, to create table
Oracle and MYSQL difference between
Oracle is a multi-user, multi-MYSQL database
1. follow the SQL standard
2 different manufacturers, different database products, but have their own dialect
3. use their own dialect, can perform the same function
4. Oracle security level is higher, MYSQL open source free
* from Tab SELECT;
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Database ---> database instance ---> tablespaces (logical units) (user) ---> data file (physical units)
of a country earth ---> ---> Department ( logical units) (citizen) ---> mountains and rivers (physical unit)
normally, ORacle database will be only one instance ORCL,
a new project:
MYSQL: create a database, create a corresponding table
Oracle: create a table space, create a user, the user to create tables
Oracle and MYSQL difference between
Oracle is a multi-user, multi-MYSQL database
1. follow the SQL standard
2 different manufacturers, different database products, but have their own dialect
3. use their own dialect, can do the same thing
4. Oracle security level is higher, MYSQL open source free
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basic query:
SQL: structured query language
Please listen to the question: Tell me about the classification and each type of SQL operators What are common
four categories:
DDL: data Definition language drop the ALTER TRUNCATE the Create
DML: data manipulation language Update the Delete INSERT
DCL: data control language grant revoke authorization safety
DQL: select from data query language clause where clause of
the query structure:
SELECT [Column Name] [*] from table [where Condition] [group by grouping condition] [HAVING filter] [order by sorting]
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SELECT from EMP *;
SELECT +. 1. 1; - the Oracle being given equal, the output is in MYSQL 2
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Dual: Oracle the virtual table, a pseudo-table, a syntax structure is mainly used padded
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SELECT. 1. 1 + Dual from;
the SELECT * from Dual;
the SELECT 1 from emp;
- often a direct write * to write efficient than
the SELECT COUNT from emp (1);
the SELECT COUNT (*) from emp;
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alias query: use as keywords, can be omitted
alias can not have special characters or keywords, if you double quotes
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the SELECT ename name, sal emp wages from;
the SELECT ename "name", sal emp wages from;
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remove duplicate data distinct
multi-column to remove duplicate: each column is repeated as to be able to count
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- single row remove duplicates
SELECT DISTINCT Job from EMP;
- a plurality of rows of deduplication
SELECT DISTINCT Job, DEPTNO from EMP;
- four arithmetic query
SELECT. 1. 1 + from Dual;
- - Polling staff salary = monthly 12 *
the SELECT SAL * 12 from emp;
- inquiry staff salary + bonus
the SELECT SAL + COMM 12 * from emp;
--nvl function: 1 if the argument is null is returned parameter 2
the SELECT SAL * 12 + NVL (COMM, 0) from EMP;
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NOTE: null value, representative of an ambiguous unpredictable, four arithmetic operations can not be done
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string concatenation:
Java: number + stitching
Oracle-specific connector: | | stitching
in Oracle, mainly double-quotes when using an alias, single quote is the value used is the character
concat (str1, str2) function, in both the mysql and Oracle
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- query the employee name: name: SCOTT
ename from EMP SELECT;
- spliced character
select 'Name:' || ename from EMP;
- the name of the query in a range of employee information ( 'JONES', 'SCOTT' , 'FORD') in
- splicing using the function
select concat ( 'Name:', ename) from EMP;
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Condition Query: [where the latter wording]
relational operators:>> = = <<= = <!>
Logical operators: and or not
other operators:
like fuzzy query
in (set) in a set
between .. and .. in a certain interval
is null is empty is determined
is not null determined not empty
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- can query a monthly bonus employee information
the SELECT * from emp the WHERE COMM iS not null;
- query wage employee information between 1500--3000
the SELECT * from emp the WHERE SAL the bETWEEN 1500 and 3000;
the SELECT * from emp the WHERE SAL> = 1500 and SAL < 3000 =;
SELECT * from EMP WHERE ename in ( 'JONES', 'SCOTT', 'FORD');
_ matches a single character
'JONES', 'SCOTT', 'FORD');
if there are special characters, use the escape escaping
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Fuzzy query: like
% with a character
- queries employee name first three characters are O employee information
the SELECT * from emp the WHERE ename like '__O%';
- employee name query, the information contained percent of employees
select * from emp where ename like ' % \ %%' escape '\';
* from EMP WHERE ename SELECT like '% # %%' Escape '#';
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Sort: order by
ascending: asc ascend
descending: desc descend
Sort problem null Note: nulls first | last
simultaneously arranged in a plurality of rows, separated by commas
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- query employee information, in accordance with the bonus descending sorting
select * from emp order by comm desc nulls last;
- Query department number and wages in accordance sorted by department ascending, descending sort wages
DEPTNO SELECT, SAL by DEPTNO from EMP Order ASC, SAL desc;
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Function: The return value must be
one-way function: on a value in a row is processed
numerical function
character function
date function
conversion function
general functions
multi-line functions: process all rows of a column
max () min COUNT sUM AVG
1. simply ignore null values
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- the sum of wages and salaries statistics
the SELECT sUM (SAL) from emp;
- the sum of the statistical employee bonus 2200
the SELECT sUM (COMM) from emp;
- statistics number of employees 14
the SELECT COUNT (1) from emp;
- an average of 550 employees bonuses statistical error = 2200/14
the SELECT AVG (COMM) from emp;
- the statistical average bonuses of employees 157. the
the SELECT SUM (COMM ) / COUNT (from EMP. 1);
SELECT ceil (SUM (COMM) / COUNT (. 1)) from EMP;
Update EMP SET ename = '% TUR the NER' WHERE ename = 'TURNER';
select * from emp;
--数值函数
select ceil(45.926) from dual; --46
select floor(45.926) from dual; --45
--四舍五入
select round(45.926,2) from dual; --45.93
select round(45.926,1) from dual; -- 45.9
select round(45.926,0) from dual; --46
select round(45.926,-1) from dual; --50
select round(45.926,-2) from dual; --0
select round(65.926,-2) from dual; --100
--截断
select trunc(45.926,2) from dual; --45.92
select trunc(45.926,1) from dual; -- 45.9
select trunc(45.926,0) from dual; --45
select trunc(45.926,-1) from dual; --40
select trunc(45.926,-2) from dual; --0
the trunc SELECT (65.926, -2) from Dual; --0
--求余
select mod(9,3) from dual; --0
SELECT MOD (9,4) from Dual; --1
- Character Function
- substr (str1, start index, length)
- Note: The starting index Whether writing is 0 or 1, taken from the first character
SELECT substr ( 'ABCDEFG', 0,3) from Dual; - ABC
SELECT substr ( 'ABCDEFG', l, 3) from Dual; - ABC
SELECT substr ( 'ABCDEFG', 2,3) from Dual; --bcd
- Get string length 28 24
SELECT length ( 'ABCDEFG') from Dual;
- removing space characters on both sides of the left and right
select trim ( 'hello') from dual ;
- replacement string
the Select replace ( 'Hello', 'L', 'a') from Dual;
- date function
- to today's date query
SELECT SYSDATE from Dual;
- query today's date, three months after
select add_months (sysdate, 3) from dual;
- Query 3 days after the date of
select sysdate + 3 from dual;
- Polling staff recruited days
the SELECT sysdate - the HireDate from emp;
the SELECT ceil (sysdate - the HireDate) from emp;
- Query hires a number of weeks
the SELECT (sysdate - the HireDate) / 7 from emp;
- Query hires month the number of
the SELECT MONTHS_BETWEEN (sysdate, the HireDate) from emp;
- query hires year
the SELECT MONTHS_BETWEEN (sysdate, the HireDate) / 12 from emp;
- conversion function numerical value date transfer switch characters characters
- characters turn value to_number (str) tasteless
select 100 + '10 'from dual; --110 default has helped us convert
the SELECT 100 + to_number ('10') from Dual; - 110
- numeric characters turn
select to_char (sal, '$ 9,999.99 ') from emp;
TO_CHAR SELECT (SAL, 'L9,999.99') from EMP;
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TO_CHAR (1210.73, '9999.9') return '1210.7'
TO_CHAR (1210.73, '9,999.99') returns' 1,210.73'
to_char (1210.73, '$ 9,999.00' ) return '$ 1,210.73'
TO_CHAR (21 is, '000099') return '000021'
TO_CHAR (852, 'XXXX') return '354'
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- Date revolution character TO_CHAR ()
SELECT TO_CHAR (SYSDATE , 'mm-dd-YYYY HH: mi The: SS') from Dual;
select to_char (sysdate, 'YYYY-mm-dd HH24: mi The: SS') from Dual;
- you want in
select to_char (sysdate, ' yyyy ') from Dual; --2 017
- just want the date
select to_char (sysdate,' d ' ) from dual; --2 represents a day of the week
select to_char (sysdate,' dd ' ) from dual; - -10 represents the first few days of the month
select to_char (sysdate, 'ddd' ) from dual; --100 represents the first day of the year
the SELECT the TO_CHAR (sysdate, 'Day') from Dual; --monday
the SELECT the TO_CHAR (sysdate, 'dy') from dual;--mon week shorthand
- character transfer date
to_date the SELECT ( '2017-04-10', 'yyyy-mm-dd') from Dual;
- Query 1981 --1985 annual income recruits information
select * from emp where hiredate between to_date ( '1981', 'yyyy ') and TO_DATE (' 1985 ',' YYYY ');
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generic function:
NVL (parameter 1, parameter 2) If parameter 1 = null return parameter 2
NVL2 (parameter 1, parameter 2, parameter 3) If parameter 1 = null, 3 returns to the parameter, the parameter 2 otherwise
NULLIF (parameter 1, parameter 2) If parameter 1 = 2 then return null parameter, otherwise parameter 1
COALESCE: returns a non-null value
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SELECT NVL2 (null, 5,6) from Dual; --6;
SELECT NVL2 (1,5,6) from Dual; --5;
SELECT NULLIF (5,6) from Dual; --5
SELECT NULLIF (6,6) Dual from; --null
SELECT COALESCE (null, null, 3,5,6) from Dual; --3
SELECT ceil (-12.5) from Dual; --12
SELECT Floor (12 is.5) from dual; --12
select ' hello ' from dual;
select * from emp;