PRIMARY KEY Table Constraint
Table constraint to define table's Primary Key
PRIMARY KEY <expr> TAG <cTagName> [COLLATE <cCollateSequence>]
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.
The PRIMARY KEY table constraint is used to define <expr> as the table's Primary Key. 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>. If a table already has a primary key defined, an error will be returned.
The optional COLLATE <cCollateSequence> clause is included for Visual FoxPro language compatibility only.
CREATE TABLE newcust; (acc_ref char(5) default strzero(seqno(),5),; acc_name char(20)) ALTER TABLE newcust; ADD PRIMARY KEY acc_ref+acc_name TAG RefName
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