functii predefinite uzuale in sql
DESCRIPTION
BAZE DE DATE AVANSATE - SQL SERVER 2008TRANSCRIPT
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Functii predefinite uzuale in SQL Server
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Functia CONVERT coverteste rezultatul unei expresii intr-un anumit timp de date
Sintaxa:
CONVERT (tip_date_rezultat [(lungime)], expresie [, stil_coversie])
tip_date_rezultat – tipul de date in care se converteste expresie lungime – lungimea tipului de date, doar pentru tipurile de date care suporta expresie – orice expresie admisibila SQL, al carei rezultat se va converti in tip_date_rezultat stil_conversie – cod folosit atunci cand se doreste utilizarea unor modele de conversie SQL;
Cod Format data/ora rezultat
101 mm/dd/yyyy
103 dd/mm/yyyy
108 hh:mi:sec
113 dd mon yyyy hh:mi:ss:mmm
Cateva coduri uzuale pentru stil_conversie pentru conversia in/din data/ora:
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Functia CONVERT (exemple)
Nota: In acest caz codul 103 indica in ce mod este specificata data in sirul de caractere (dd/mm/yyyy) pentru a fi corect convertita in formatul datei serverului ! Daca se doreste afisarea in formatul dd/mm/yyyy, o data calendaristica trebuie convertita in sir de caractere, cu cod 103, asa cum este in primul exemplu, altfel se afiseaza in formatul serverului.
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Functia CONVERT (exemple)
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Functia GETDATE()
returneaza data si ora serveruluiExemplu: data si ora serverului
Exemplu: data serverului
Exemplu: ora serverului
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Functia NEWID() returneaza o valoare de tip UNIQUEIDENTIFIER
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Functiile DAY, MONTH, YEAR
DAY (expresie) MONTH(expresie) YEAR(expresie)
Sintaxa:
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Functia DATEPART
DATEPART (informatie_calendaristica, expresie_data/ora)
Extrage dintr-o data calendaristica/ora o anumita informatie calendaristica, identificata printr-un cod
Sintaxa:
Cod informatie_calendaristica (cateva valori uzuale)
Rezultat
year An
month Luna
day Zi
dayofyear Numar zi din an
quarter Trimestru
week Numar saptamana din an
hour Ora
minute Minutele
second Secundele
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Functia DATEPART (exemple)
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Functia DATEDIFF
DATEDIFF (informatie_calendaristica, data/ora start, data/ora final)
Calculeaza diferenta dintre doua date calendaristice (data/ora final si data/ora start). Rezultatul este furnizat intr-un anumit tip de informatie calendaristica, identificata printr-un cod
Sintaxa:
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Functia DATEADD
DATEADD (informatie_calendaristica, n, data/ora start)
Calculeaza o data calendaristica, pornind de la o anumita data (data/ora final ) la care se adauga un n (in format informatie calendaristica)
Sintaxa:
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Functiile LTRIM, RTRIM LTRIM(expresie) – elimina spatiile nesemnificative de la stanga unei expresii de tip sir de caractere
RTRIM(expresie) – elimina spatiile nesemnificative de la dreapta unei expresii de tip sir de caractere
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Functiile LEN, LOWER, UPPER LEN(expresie) – returneaza numarul de caractere dintr-o expresie
LOWER(expresie) – returneaza sirul de caractere din expresie scris cu litere mici
UPPER (expresie) – returneaza sirul de caractere din expresie scris cu litere mari
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Functiile LEFT, RIGHT, SUBSTRING LEFT(expresie, n) – returneaza n caractere de la stanga unei expresii sir de caractere
RIGHT(expresie, n) – returneaza n caractere de la dreapta unei expresii sir de caractere
SUBSTRING (expresie, start, n) – returneaza n caractere dintr-o expresie sir de caractere, incepand de la pozitia start
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Functia CASE
CASE expresieAWHEN expresieB1 THEN expresie_Rezultat[WHEN expresieB2 THEN expresie_Rezultat]…[ELSE expresie_Rezultat_F]
END
Sintaxa varianta 1:
CASEWHEN expresie_logica1 THEN expresie_Rezultat[WHEN expresie_logica2] THEN expresie_Rezultat…[ELSE expresie_Rezultat_F]
END
Sintaxa varianta 2:
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Functia CASE (exemplu varianta 1)
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Functia CASE (exemplu varianta 2)