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==Purpose== Table constraint to define table's Primary Key ==Syntax== PRIMARY KEY <expr> TAG <cTagName> [COLLATE <cCollateSequence>] ==See Also== [[ALTER TABLE]], [[SQL Constraints|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. 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. ==Example== <code lang="recital"> set sql to vfp 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 list structure index </code> ==Products== Recital, Recital Server [[Category:Documentation]] [[Category:SQL]]

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