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SQL handleiding

SQL TUIS SQL Inleiding SQL-sintaksis SQL Kies SQL Kies Distinct SQL Waar SQL En, of, nie SQL Bestel deur SQL Voeg in SQL nulwaardes SQL-opdatering SQL verwyder SQL Kies Top SQL Min en Max SQL-telling, gemiddeld, som SQL Soos SQL Wildcards SQL in SQL Tussen SQL aliasse SQL sluit aan SQL Inner Sluit aan SQL Links Sluit aan SQL Reg Sluit aan SQL Volledige Aansluiting SQL Self Sluit aan SQL Unie SQL Groep deur SQL het SQL bestaan SQL Enige, Almal SQL Kies In SQL Voeg in Kies SQL-geval SQL nul-funksies SQL gestoorde prosedures SQL opmerkings SQL-operateurs

SQL- databasis

SQL Skep DB SQL Drop DB SQL Backup DB SQL Skep tabel SQL Drop Tabel SQL Verander Tabel SQL-beperkings SQL nie nul nie SQL Uniek SQL Primêre Sleutel SQL buitelandse sleutel SQL Check SQL verstek SQL-indeks SQL Outo-verhoging SQL datums SQL-aansigte SQL-inspuiting SQL Hosting SQL-datatipes

SQL- verwysings

SQL sleutelwoorde
ADD ADD CONSTRAINT ALTER ALTER COLUMN ALTER TABLE ALL AND ANY AS ASC BACKUP DATABASE BETWEEN CASE CHECK COLUMN CONSTRAINT CREATE CREATE DATABASE CREATE INDEX CREATE OR REPLACE VIEW CREATE TABLE CREATE PROCEDURE CREATE UNIQUE INDEX CREATE VIEW DATABASE DEFAULT DELETE DESC DISTINCT DROP DROP COLUMN DROP CONSTRAINT DROP DATABASE DROP DEFAULT DROP INDEX DROP TABLE DROP VIEW EXEC EXISTS FOREIGN KEY FROM FULL OUTER JOIN GROUP BY HAVING IN INDEX INNER JOIN INSERT INTO INSERT INTO SELECT IS NULL IS NOT NULL JOIN LEFT JOIN LIKE LIMIT NOT NOT NULL OR ORDER BY OUTER JOIN PRIMARY KEY PROCEDURE RIGHT JOIN ROWNUM SELECT SELECT DISTINCT SELECT INTO SELECT TOP SET TABLE TOP TRUNCATE TABLE UNION UNION ALL UNIQUE UPDATE VALUES VIEW WHERE
MySQL-funksies
String Functions: ASCII CHAR_LENGTH CHARACTER_LENGTH CONCAT CONCAT_WS FIELD FIND_IN_SET FORMAT INSERT INSTR LCASE LEFT LENGTH LOCATE LOWER LPAD LTRIM MID POSITION REPEAT REPLACE REVERSE RIGHT RPAD RTRIM SPACE STRCMP SUBSTR SUBSTRING SUBSTRING_INDEX TRIM UCASE UPPER Numeric Functions: ABS ACOS ASIN ATAN ATAN2 AVG CEIL CEILING COS COT COUNT DEGREES DIV EXP FLOOR GREATEST LEAST LN LOG LOG10 LOG2 MAX MIN MOD PI POW POWER RADIANS RAND ROUND SIGN SIN SQRT SUM TAN TRUNCATE Date Functions: ADDDATE ADDTIME CURDATE CURRENT_DATE CURRENT_TIME CURRENT_TIMESTAMP CURTIME DATE DATEDIFF DATE_ADD DATE_FORMAT DATE_SUB DAY DAYNAME DAYOFMONTH DAYOFWEEK DAYOFYEAR EXTRACT FROM_DAYS HOUR LAST_DAY LOCALTIME LOCALTIMESTAMP MAKEDATE MAKETIME MICROSECOND MINUTE MONTH MONTHNAME NOW PERIOD_ADD PERIOD_DIFF QUARTER SECOND SEC_TO_TIME STR_TO_DATE SUBDATE SUBTIME SYSDATE TIME TIME_FORMAT TIME_TO_SEC TIMEDIFF TIMESTAMP TO_DAYS WEEK WEEKDAY WEEKOFYEAR YEAR YEARWEEK Advanced Functions: BIN BINARY CASE CAST COALESCE CONNECTION_ID CONV CONVERT CURRENT_USER DATABASE IF IFNULL ISNULL LAST_INSERT_ID NULLIF SESSION_USER SYSTEM_USER USER VERSION
SQL Server funksies
String Functions: ASCII CHAR CHARINDEX CONCAT Concat with + CONCAT_WS DATALENGTH DIFFERENCE FORMAT LEFT LEN LOWER LTRIM NCHAR PATINDEX QUOTENAME REPLACE REPLICATE REVERSE RIGHT RTRIM SOUNDEX SPACE STR STUFF SUBSTRING TRANSLATE TRIM UNICODE UPPER Numeric Functions: ABS ACOS ASIN ATAN ATN2 AVG CEILING COUNT COS COT DEGREES EXP FLOOR LOG LOG10 MAX MIN PI POWER RADIANS RAND ROUND SIGN SIN SQRT SQUARE SUM TAN Date Functions: CURRENT_TIMESTAMP DATEADD DATEDIFF DATEFROMPARTS DATENAME DATEPART DAY GETDATE GETUTCDATE ISDATE MONTH SYSDATETIME YEAR Advanced Functions CAST COALESCE CONVERT CURRENT_USER IIF ISNULL ISNUMERIC NULLIF SESSION_USER SESSIONPROPERTY SYSTEM_USER USER_NAME
MS Access-funksies
String Functions: Asc Chr Concat with & CurDir Format InStr InstrRev LCase Left Len LTrim Mid Replace Right RTrim Space Split Str StrComp StrConv StrReverse Trim UCase Numeric Functions: Abs Atn Avg Cos Count Exp Fix Format Int Max Min Randomize Rnd Round Sgn Sqr Sum Val Date Functions: Date DateAdd DateDiff DatePart DateSerial DateValue Day Format Hour Minute Month MonthName Now Second Time TimeSerial TimeValue Weekday WeekdayName Year Other Functions: CurrentUser Environ IsDate IsNull IsNumeric
SQL Vinnige Verw

SQL voorbeelde

SQL voorbeelde SQL vasvra SQL-oefeninge SQL-sertifikaat

SQL WHERE klousule

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Die SQL WHERE klousule

Die WHEREklousule word gebruik om rekords te filter.

Dit word gebruik om slegs daardie rekords te onttrek wat aan 'n gespesifiseerde voorwaarde voldoen.

WAAR Sintaksis

SELECT column1, column2, ...
FROM table_name
WHERE condition;

Let wel: Die WHEREklousule word nie net in SELECTstellings gebruik nie, dit word ook gebruik in UPDATE, DELETE, ens.!

Demo databasis

Hieronder is 'n keuse uit die "Klante"-tabel in die Noordewind-voorbeelddatabasis:

CustomerID CustomerName ContactName Address City PostalCode Country
1

 Alfreds Futterkiste Maria Anders Obere Str. 57 Berlin 12209 Germany
2 Ana Trujillo Emparedados y helados Ana Trujillo Avda. de la Constitución 2222 México D.F. 05021 Mexico
3 Antonio Moreno Taquería Antonio Moreno Mataderos 2312 México D.F. 05023 Mexico
4

 Around the Horn Thomas Hardy 120 Hanover Sq. London WA1 1DP UK
5 Berglunds snabbköp Christina Berglund Berguvsvägen 8 Luleå S-958 22 Sweden

WAAR Klousule Voorbeeld

Die volgende SQL-stelling kies al die kliënte van die land "Mexico" in die "Klante"-tabel:

Voorbeeld

SELECT * FROM Customers
WHERE Country='Mexico';

Teksvelde vs. Numeriese velde

SQL vereis enkele aanhalingstekens rondom tekswaardes (die meeste databasisstelsels sal ook dubbele aanhalingstekens toelaat).

Numeriese velde moet egter nie in aanhalingstekens ingesluit word nie:

Voorbeeld

SELECT * FROM Customers
WHERE CustomerID=1;

Operateurs in die WAAR-klousule

Die volgende operateurs kan in die WHEREklousule gebruik word:

Operator Description Example
= Equal
> Greater than
< Less than
>= Greater than or equal
<= Less than or equal
<> Not equal. Note: In some versions of SQL this operator may be written as !=
BETWEEN Between a certain range
LIKE Search for a pattern
IN To specify multiple possible values for a column

Toets jouself met oefeninge

Oefening:

Kies alle rekords waar die Citykolom die waarde "Berlyn" het.

SELECT * FROM Customers
  = ;


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