Difference between revisions of "UNIQUE Table Constraint"
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==Example== | ==Example== | ||
<code lang="recital"> | <code lang="recital"> | ||
| − | + | CREATE TABLE newcust; | |
| − | CREATE TABLE newcust (acc_ref char(5) default strzero(seqno(),5), acc_name char(20)) | + | (acc_ref char(5) default strzero(seqno(),5),; |
| − | ALTER TABLE newcust ADD UNIQUE acc_ref+acc_name TAG RefName | + | acc_name char(20)) |
| − | + | ALTER TABLE newcust; | |
| + | ADD UNIQUE acc_ref+acc_name TAG RefName | ||
| − | + | CREATE TABLE contact; | |
| − | CREATE TABLE contact (ContRef char(5), LastName char(25), FirstName char(25), | + | (ContRef char(5), LastName char(25), FirstName char(25),; |
| − | UNIQUE FullName (LastName, FirstName, ContRef)) | + | UNIQUE FullName (LastName, FirstName, ContRef)) |
</code> | </code> | ||
Latest revision as of 11:16, 22 December 2009
Purpose
Table constraint to define a candidate index
Syntax
UNIQUE <expr> TAG <cTagName> [COLLATE <cCollateSequence>]
UNIQUE [<cTagName>] (column1[column2,…])
See Also
ALTER TABLE, CONSTRAINTS, CREATE TABLE
Description
A constraint is used to define rules that help to provide data integrity. TABLE constraints apply to table-based operations. You must have ALTER privilege on the table. The table will be locked for EXCLUSIVE use during the operation.
UNIQUE <expr> TAG <cTagName> The UNIQUE table constraint is used to define <expr> as a candidate index for the table. The <expr> can contain any valid index key. A unique tag index is built on the specified <expr>; it is given the name as defined in <cTagName>. A table may have more than one candidate index.
COLLATE <cCollateSequence> The optional COLLATE <cCollateSequence> clause is included for Visual FoxPro language compatibility only.
UNIQUE [<cTagName>] (column1[column2,…]) The UNIQUE table constraint is used to define a unique index key. The index is built on the column or columns specified and given the name as defined in <cTagName>.
Example
CREATE TABLE newcust; (acc_ref char(5) default strzero(seqno(),5),; acc_name char(20)) ALTER TABLE newcust; ADD UNIQUE acc_ref+acc_name TAG RefName CREATE TABLE contact; (ContRef char(5), LastName char(25), FirstName char(25),; UNIQUE FullName (LastName, FirstName, ContRef))
Products
Recital, Recital Server
